Your cold spot is too hot, if you want a cool spot and a hot spot you need more than a 4 degrees variance.
You would be better off to have ambient at 86 with no hot spot than cool spot at 86 and hot spot at 90.
If you want to provide cool spot and hot spot I would recommend 76/88 and 86/88. (at least 8 to 10 degrees variance)
I like to keep gravid females a little cooler than most people their hot spot is no higher than 86/87 (Spring,fall and winter)
In the summer I actually do not provide a hot spot and simply provide ambient temps (room is around 88 which mean 86 in the tubs).
Works for me.
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