Folks, I'm wondering what's different about the water pooling in the drain pain than the water on the leaves of the live plants. Something is attracting this girl to this water source—what is it?
I notice that vitamin supplementation may be half of what it should be (monthly instead of twice monthly) but is that enough to cause a deficiency that would cause this behavior?
Salts? Does the runoff contain salts (not necessarily NaCl) from the plants or other features? Salts can stimulate thirst, and create a vicious cycle if the contaminated water "tastes" better.
faith.j.p What kind of water are you misting with (tap, distilled, RO, other)?
For the time being—or until this mystery is solved—I would put a layer of stainless steel (not aluminum; aluminum can make salts) on the bottom of the enclosure, and elevate the branch bottoms to get them out of any pooled water. The intent here is to prevent the cham from reaching and ingesting the pooled water.
Long term, I might replace that pan with one that can be drained via gravity—preventing any water from pooling and attracting the behavior.
I'm just guessing/spitballing here. Personally, I'd prefer the input of a qualified herp vet.