The front fan is blowing in?  The bottom fan is blowing up? And the top back fan is blowing out the back?
 
If the top back fan is blowing in from the back, turn the fan around so that it blows out and see what the difference is.
 
Otherwise, yeah, you need more air blowing in the front and/or up from the bottom.  You need more fans, better fans, or faster fans.

I disagree with the fact of the rear fan blowing in. Just below that fan is graphics card, and the GPUs always put out heat. Heat rises. A lot of times that heat will be pulled back into the case with the rear fan pushing air back in. I disagree fully, but it's my opinion.
 
I have it pointing outwards with the front fans pulling in to create more of a vacuum in the case to create a more push pull, with the top fans also pushing air out, it's a great effect. Works on my PC thus far.

The bottom and front fans are blowing in. My CPU fan is a Asetek 510LC Liquid Cooling CPU Cooler. Is that potentially a problem, the liquid cooler is not blowing enough air out? Unfortunately, I don't have any fan slot available, how about something like this between the cards? "StarTech.com Expansion Slot Rear Exhaust Cooling Fan" - or that would conflict with the fan of the top card?

Also plug your monitor(s) into the bottom card.

karloy
The bottom and front fans are blowing in. My CPU fan is a Asetek 510LC Liquid Cooling CPU Cooler. Is that potentially a problem, the liquid cooler is not blowing enough air out? Unfortunately, I don't have any fan slot available, how about something like this between the cards? "StarTech.com Expansion Slot Rear Exhaust Cooling Fan" - or that would conflict with the fan of the top card?

Are you sure the bottom fan is blowing air up and into the case?  In the picture, it looks like it is blowing air from inside the case down and outside the bottom of the case.  That's one backwards wired fan if it is blowing air up and in.
 
I agree with the other comments about removing the hard drive cage if possible and moving the hard drive up top into the 5 1/4" drive bay.

Switch the top and bottom cards to see if the temperature differential under load still exists. I wouldn't expect to see much of a difference with brand new cards, but you never know. Maybe the top one didn't get a good application of thermal paste.
 
EDIT: I think it's likely airflow-related, as others have suggested.

ty_ger07
Are you sure the bottom fan is blowing air up and into the case?  In the picture, it looks like it is blowing air from inside the case down and outside the bottom of the case.  That's one backwards wired fan if it is blowing air up and in.

Fans always blow towards the plastic "guard/whateverit'scalled", so it is definitely an intake.
 
Personally, I'd bet it's air-flow related as well. I like top and rear as exhaust. Front and bottom as intake. After looking at the pic again, the PSU cables really seem to block a lot of airflow.

It seems you have temperature issue inside your case.
Two cards emitting a lot of heat inside the case and one fan cannot take it out.
The cold air is going in by two fans then heated by GPU's and one fan trying to take it out but air temperature inside the case is going up.
If it possible to take HDD bay out and move HDD to up, then move CPU heat sink with fan to the front. Change fan so now it intakes the cold air through radiator. (I don't know if it is possible to do).
Then change back and bottom fans to take the air out.
Also you can check the option to change 2 airflow fans to Noctua NF-F12.

LittleGuy
For me, I would move the hard drives to the 5.25 bay and if you can remove the hard drive bay I would. It will help not block the fans in front. I would also tidy up the power supply cables.

Next I would run with the side panel off and that helps drop the temps than it's an air problem. Then I would consider better fans. If that does not help I would reapply the TIM. On the card, but I think it's an air issue myself.

+1. This is something worth trying. For troubleshooting you can always lay your hard drive on the bottom of the case and check your temps with the cage removed and the cables tidied.

I'm also going to mention this in the "Higher temps for The Witcher 3" thread since it applies to both and I don't want anyone to miss it.
 
Last night after moving to the latest driver (368.81) in the afternoon, I started to notice frankly terrible performance in Witcher 3 with SLI. It looks like most of this has to do with the DPC latency issue that has come to light and which Nvidia has a hotfix for (doesn't apply to SLI). Along with the terrible performance came really high temps in my top card. I'm talking 10-15 degrees more than it was in my previous tests. Even after I disabled SLI, I found my main card still running hotter than it did before.
 
So this morning I roll back to 368.39 and once again performance in Witcher 3 is back up to where it was and again the temps were back down to what I had seen before. Yes, it could very well be airflow in your case but this is something to look at.
 
TL;DR  If it seems to be more than the airflow, take a look at your drivers. 368.39 are running better and cooler on my machine.

I tried to SLI ACX coolers before... Sent them right back too... ACX cards are not the greatest for SLI. 

Should help, but still expect about a 10-15° gap. Pretty normal in open air coolers.

Blower style coolers ftw. 

Caust
Always remember, when it comes to temps in sli it goes: water > blower > open air designs

Definitely varies with multiple factors. Open air designs and blower all depend on the type of case you have, how many fans you have, and how good the vacuum to pull the air away is.

gregoryv

karloy

ragevirusqq
I would save a few dollars up and buy a new case. Its a shame to choke that sli setup with not enough airflow. Great airflow cases can be had for less than a hundred bucks. Corsair air 540, Fractal design define s, NZXT come to mind. Corsair cases can be found at Frys too if you have one near you. There is lots of good options even in the 60 - 80 dollar price range.   
 
You have great gear in there. It just needs a nice comfy place to live. 

Alright, after plenty of research I am going to upgrade my case to a Corsair’s Graphite Series 760T. My old case has airflow issues per reviews. Going to have 2 x 140 fans in the front, one 120 at the bottom, Asetek 510LC 120mm fan in the back, 140 fan at the top. Hopefully that will do it ;-)

Good choice. Corsair 760T is great case. I am having 750D flow edition and it is great.
You don't need to use fan on the bottom.
You have 2x140 fans on the front and 1x140 fan on the back coming with case.
Also you have additional place on the top to put CPU cooler and fan. I would add addition 140mm fan on the top to take the hot air out.
I think it will upgrade very much the flow inside the case and temperatures on the both cards will go down.
 

Very helpful, thanks for the advice. I have 1x CPU fan, and 4x case fan plugs on my board. 
 
What is the ideal inbound/outbound fan ratio? 
 
You are recommending: 
 
Bottom: None
Front: Two fans (already installed) - inbound
Back: Fan (already installed) - outbound
Top: CPU cooler fan + additional fan - outbound
 
(2x inbound, 3x outbound)
 
I wanted to do the following: 
 
Bottom: Fan - inbound
Front: Two fans (already installed) - inbound
Back: Fan (already installed) - outbound
Top: CPU cooler fan - outbound
 
(3x inbound, 2x outbound)
 
First time configuring this ;)