Anything past 87 degrees and they don't conduct photosynthesis as well as they are trying to re-coup from the heat they didn't enjoy, but like another poster said... they do just fine outdoors when the temps go over 100 degrees sometimes.
I shoot to keep things under 85, you should try to as well. Also, don't test the temps from the soil, test it from your canopy... this is what's really important... how warm is it near the tops of the plants. If you have super tall plants you could realize that the temps are indeed peaking at over 90 in the canopy while they are 85 in the soil so it's important to remember to check the canopy.
Maybe try a small fan blowing air across your hoods? I nkow you are air cooled but alot of the time just moving air right underneath the glass of your lamp will cool it down a tad. Good luck.
Let the good times roll!!