I want to say air temp. The thermometer/hygrometer is shown in one of my most recent pics. I have it set on top of a dragon statue that sits on the floor underneath the light, next to the plants. The light is about a foot away from the canopy; which might be too close but I'm using a cool-tube so I thought that I would try to get the light as close to the canopy as possible. Anyway, this didn't start until I put the HPS in the cool-tube. I am considering leaving the tent door unzipped part of the way to increase ventilation but haven't decided yet. The lights are off right now so I'd like to see if the temps return back to "average" with the lights off and to monitor whether the temp rises again once the light turns back on or not. I'm wondering if my air scrubber is shot and that is contributing to the rise in the temps too. Otherwise, the plants don't seem to mind. Two of the three, Skywalker and C99x, both seem to not mind the increased temps and my AxT (S1) might be shot, but the jury is still out on that. Another theory I have is that because these plants are smaller, there is a shorter distance between the light and the reflective floor of the tent which may increase the temps. It seems that when I used my Tron in the past couple of comparatives that it seemed to get really hot inside the Tron, but I didn't have a thermometer to monitor the temps so I really don't know if it was 90+ degrees inside the Tron or not. I'll keep an eye on it and if things don't improve, or get worse, then I'll panic. But for now, or at least a little while ago, they look like they are adjusting just fine.
Thanks for chiming in y'all, I really appreciate your feedback.