Ambient temp of 80 is fine. As long as the hot spot is where it should be. If your heat pad is set to 90, is the hot spot at 90? All of my UTHs are set to a higher temp in order to achieve about 90 inside the enclosure at the hot spot. Have you read over the caresheet? It really will answer a lot of questions about husbandry.
They are using a dimmer. I little low is better than to hot from a temp change.
KMG
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