If I were you... leave the heat lamp on. It's 90 degrees under the lamp, but the rest of the brooder is probably cooler, so it gives THEM the chance to choose what temperature they want. In this photo, it looks like they are "comfortable" because they are all scattered around and mostly doing chickie-type things. They're eating, drinking, moving around, and falling asleep in a small pile with each other. That's perfect. When a hen takes care of the chicks, they spend VERY little time underneath her after the first three days or so. Once they get out of the nest and learn to walk, eat, forage, etc., they usually only go under her at night. On chilly days, she'll stop in the middle of nowhere and let them get back under her for a bit to warm up. And then it's back out to forage and play. So the fact that they aren't under the heat lamp, tells me it's not too cold. And doing normal chickie things tells me it's not actually too hot either. Plus the little small pile of sleeping chicks next to the water says they aren't too hot - because they still pile up to sleep. Well, mostly. Lol! HOWEVER, when you turned the heat lamp off and they all suddenly snuggled up underneath where it was and got into a tight bunch, that told me it might be too chilly. So leave the heat lamp on, and you can leave it at the height it is at, too. Just make sure they have room to get away from it, like you seem to have done, and don't put the food or water under it (which you've also done). They're fine where they are.