Sorry for no update, guys! I totally thought her new issue was unrelated. Turns out they were related and I'm clueless about chickens. To be honest I kind of went and hid with my tail between my legs for a few days. Rough few days, but better now!

(Not your guys' fault in any way)
I actually do a full cage change every three days, and change the paper towels every morning and night. They're just little poop machines.
For those wanting to know the outcome, I thought she was having behavior issues. She was eating/drinking, not not from her assigned dishes. I thought it was a learned thing. Turns out she was still sick! I ended up roasting her little butt for a while. She stayed in felt snuggled against me on a heating pad for nearly 24 hours. The average temp inside was upwards of 105F. Anything lower and she got cold and shivered.
After 24 hours or so she perked right up. She doesn't scream anymore, drinks, eats, and even runs around and steals food from the other babies. Including the mealworms for the older babies. I know babies that young shouldn't have treats, so I kept trying to catch her to take it away. She was so happy running around and peeping with it I eventually gave up. Until a few days ago she had no interest in eating them anyway.
She's now a happy, normal chicken! She hardly spends any time in her heating cave, eats normally, plays, and is just a happy little girl. The only side effect of all the work is that for now she's easier to handle. She doesn't WANT to be held, but she won't run away from my hand in terror.
All the other babies turned out to be normal and fine, luckily! My older babies learned to escape their cage, find the - not very well hidden - mealworm farm and.... Yeah. We've banned mealworms. The gecko's are now in the back of the fridge until I need them.
So I owe you guys a HUGE debt and a THANK YOU. I swore the second time it was just that she had an attitude. I didn't know she was still sickly. This site managed to save her tiny little butt twice.

And now she's a cranky little baby who steals things from the other babies.
She's also learned the joys of a grit bath. Ava did a weird little breakdance on the floor in the grit, Angry Baby followed, and now she happily sits in it and peeps. Hasn't figured out the breakdancing aspect yet, but she knows how to peep. She's like the younger sibling all the older ones just put up with. She's a bit needy and clingy, but happy.