Thats fine. I wasn't able to get my rack to heat up properly. Bottom level varied a decent amount more (B:87/T:91) from the top so I had to turn it up. My temps are the same as you and all mine are fine. I also wonder what will burn them. I did notice when I was using my dimmer when it would get past 96+ they all would move off of it. 90 seems to be just right.