I go by overall temps inside the box too.
If I stick my thermometer under the light it will hit 88 - 90, anywhere else inside its 77/82.
From what I read they stop, or slow growth after 85, so I dont see that happening. My temps have not changed, and if they are slowed in growing thats a good thing, cause I'd be out of room lol...
The two pics I posted were taken 21 days apart from what my folders show..