My fish do the same thing. Last year I was hitting 99f on top before aeration and they were doing good. I run strictly at night for 9 hours and my temps are low 80s with just a couple degrees difference top to bottom in 11'. I've also added dye this year to help shade the deeper water. I dont know the answer to the question, but by the time you find out, it may be too late.

.10 surface acre pond, 10.5 foot deep. SW LA. The epitome of a mutt pond. BG, LMB, GSF, RES, BH, Warmouth, Longear Sunfish, Gambusia,Mud Minnows, Crappie, and now shiners!!...I subscribe!!