I'm no expert with bloods, but I doubt they need 90% humidity all of the time. They seem to be a "middle" snake in temps and humidity, where moderate plus humidity will work, like 70%-80%. A friend has a few, and they are very healthy as far as I know. He has never had them at 90% humidity. But they do not experience lower than 60% either.

Cooler temps with a drop in humidity will surely result in not feeding. Glass tanks with screen tops are pretty much a no-no for bloods, unless perhaps the room is heated.