I think, with the three diffusers, you should immediately reduce your run time to 9 hours. Continue to monitor you DO levels, and as long as they stay good, continue to cut back on your start time to allow your surface temps as much time as possible to cool. I've cut mine back again for the same reason. Not quite 90 yet, but really close.

Regarding infusing a cool/cold rain, you have to be careful. If the temp drops too quickly you'll stress your fish. Better to let it mix in naturally IMO, than to force it to mix.

.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!!