Animal Plastics T8 Heat Range

I have had an AP T8 for a few months now. I have a RHP from ProProducts (installed before AP delivered to me) and a vivarium VE-100 thermostat. At first, it was great, no issues. But recently, I have not been able to keep a good heart range. There is always only a 3-4 degree range. Meaning, right now, the warm side is 87 degrees and the cold side is 83 degrees. I prefer to keep each side a little warmer or a little cooler, respectively. I am not sure how to fix this. Anyone else run into this problem and have any luck with getting a better gradient? Thanks!

What side do you keep the thermostat's probe?

I find that in a cool room (ambient below 75F) the probe needs to be on the cool side. In warm weather (temps above 75F) the probe needs to be on the warm side. Otherwise I experience exactly the same as you.

Maybe the change of seasons is the culprit!

So are trying to have your war side hotter while keeping your cool side cooler? I guess I'm not understanding the issue.

As long as your ambient temps are around 80 degrees, you should be good.

I have the same set up but a T10 instead of T8. I have my thermostat prob dangling under the RHP and set to 90. My temps on warm side reads 90 and thermometer on cool side reads 80.. where is your thermostat set up and to what temp?