first things to check...
substrate. if you are using sand as a substrate this could be a case of impaction. but if shes pooping in the bath, probably not impaction.
size of prey. she may not be digesting insects properly if they are too big. you mentioned you went to smaller insects. this was a good idea. just keep an eye on her now.
the temps in the cool, hot, and basking spots. basking spots should be around 105-115 depending on who you ask. for my dragons i get them around 115. 110 for adults. cool spots around 70.
UVB light should be provided throughout the entire cage not just basking spot.
sounds like shes hydrated well as you bathe her and mist her like you say. try maybe putting a water dish in her cage where she can get in a poop, cause you said she does in the bathtub. warm water like in a bath relaxes dragons so yes they will poop alot in water. this is normal
make sure shes getting the calcium and vitamins as needed. and
and make sure you are offering plenty of greens as well. try some romaine lettuce, dragons seems to love it, even tho its not great in nutrition compared to other greens. it also helps with passing stools. squash is also another good one.
if you see no improvement, a vet check is worth it
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Beach Beardies
2.2. bearded dragons
1.1. Sugar Gliders
0.2. Felines *queen athena and missy*