Yeah it looks like both corners are messed up and also the one side of the sealant seems to be flaking away or something, does seem to be kind of unusual from any i have seen. Abnormal as far as i would say. 

I am thinking the yellow line SparetimePC made is just left over thermal grease.  I still suggest cleaning it with a tooth brush (gentle pressure) and rubbing alcohol.  This will clean around the SMD's and everything without risking breaking them off.  using a coffee filter or napkins or anything else is rather risky when it comes to the SMD's are the die, but the bristles on a tooth brush are perfect.
 
Use a towel or a rag to clean the excess paste removed from the surface of the Core PCB from the tooth brush occasionally, and then gently wipe it off.  
 
No matter what, a bette picture will definitely be necessary to verify.  
 
I am hoping that your GPU is still fully functional just to ease the stress of everything you are experiencing.  
 
A video I made last year on this topic:

Looks like the TIM on there.  As everyone stated, time for some cleaning.  Those corners do look odd.

The corners were chipped at some point. I would imagine that the original heatsink or waterblock were stuck on there pretty good, and you had to lever it off, rolled it over that edge, and the corners chipped.

Looks pretty plain and simple to me.

If it just happened, I hope that it still works when you put it back together.

I imagine that your video card's warranty is now void.

ty_ger07
The corners were chipped at some point. I would imagine that the original heatsink or waterblock were stuck on there pretty good, and you had to lever it off, rolled it over that edge, and the corners chipped.

Looks pretty plain and simple to me.

If it just happened, I hope that it still works when you put it back together.

I imagine that your video card's warranty is now void.

 
That's what I see also or corners chipped off from uneven tightening of the block back & forth.... if it's not put on alternating from corner to corner / little by little 

Chipped die. 

aka_STEVE_b

ty_ger07
The corners were chipped at some point. I would imagine that the original heatsink or waterblock were stuck on there pretty good, and you had to lever it off, rolled it over that edge, and the corners chipped.

Looks pretty plain and simple to me.

If it just happened, I hope that it still works when you put it back together.

I imagine that your video card's warranty is now void.

 
That's what I see also or corners chipped off from uneven tightening of the block back & forth.... if it's not put on alternating from corner to corner / little by little 

+1   uneven or Over tightened