You need to tweak the fan profile on those card. Don't run them with the default fan curve as your cards will idle back when they get up in temps.
Also would be nice to see more pics of the fans in the case.. to make sure there blowing in the right direction. I bet they mounted the cpu radiator in the front with the heat blowing onto your hot cards. Should be up top blowing hot air out and cool air and a lot of it blowing in front the front for your rad and graphics cards.
Look up jays2cents on youtube. He has a bunch of 1080 videos. One were he highlights how to adjust just the fan curve to up your cards performance and another for overclocking.. but with heat like that forget overclocking for now. You gota get those fan kicking.
Get them up to what you can bare during gaming. Try 75-85% when the temps get to 50+. Idle should be in the 30s. When your gaming they will get to the 50s-80s so it will crank the fans when needed and not after the fact when your cards are already hot in the upper 60-70 range.
Also all that heat is blowing in to your case. The founders edition 1080s were best with there blower style air cooler as it blows the heat out the back and not into your case. But your card is better thrn those.. the custom coolers are best for single cards not runing sli with all that heat in the case.
You need good exhaust to get the heat out and good cool air flow to the cards. The new evga case does a great job in that department with its added fans on the left of the cards that would blow cool air into the cards as needed. No other case does that.