Ok, you have the Comfort plate- and looks like you learned to put cling wrap on to keep it clean.

That's radiant heat. I'm going to quote Brinsea again:
"warms your chicks is through
radiant heat, which means that you won’t be able to measure the heat with a thermometer. Radiant heat passes through the air without warming it; it only warms solid objects.
The heating plate should always be safe to touch, so placing your hand on it will assure you that it is warming, and watching the behavior of the chicks should tell you whether they are happy with their brooder. Chicks will naturally huddle together if they are cool and will move away from the heat plate if they are too warm."
From an example I read, I perceive it this way: think of a day when it's not been particularly warm out, but standing in sunshine, you've said, "oh, the sun feels good." Or the dog has found a sunbeam to nap in, and if you snuggle him, he's nice and warm.
I thought at first that they had to be touching the plate. From my own experience, I hung one in the coop next to their roost, but none were actually touching it. Likewise, in the dead of winter with the door closed, it warmed me up if I stuck around long enough, and I wasn't hanging around w/my bum against it.
So I'm not sure we're giving the right advice,
@R2elk ? - stressing thermometers with radiant heat plates?
Likewise, live bodies emit radiant heat, which is why I put the plate up this yr even though the temps weren't as cold as last yr. - because I was down to only 3 birds, so they weren't benefiting from the larger flock they had been.
I hope the more experienced wisedom joins in this conversation, bc I'm thinking 26 keets in an enclosed brooder w/ANY additional heat source are going to be warm enough if not too warm. Hence, suggesting you turn off the light. I would think you could possibly even raise the plate higher. They're healthy looking and curious, bright eyed, keep an eye out for pasty butt - but I'm curious what others think of my theory.