I had mine in theirs for about that AND there were 6 others in there with them when they got sick. Turtles are amazingly adept at hiding any weakness and that includes sickness. 90f is good for an hour or so in the morning while he eats but you should let it go to 82ish hot side to 74ish cool side and if not dark, at least gloomy for most of the day. They also need cool down and complete darkness at night so no light should be used. Mine have a heat light come on at 6am and goes off at 8am. the UVB comes on at 6am and goes off at 8pm. I actually turn the thermastat in my house up to 78 when I go to work so their temps are perfect when the heat light goes off.