5 1/2 week old chick with green, sometimes watery poop

[Peachyfrog]

I have a 5 1/2 week old chick that has green, sometimes watery poop all day today. All other chicks have normal brown poop. He/she is mostly acting normal, eating and drinking. Seems to be drinking more than average at least tonight and eating but not as much as normal, likely due to all the water. Hasn't been eating anything that should have turned it's poop green, mainly just chick starter with a little dried oregano added to it. Had an earthworm I brought in from outside Friday, but that's it. Water has probiotics and acv in it. I've started mixing in a dash of dried garlic to it's food tonight too. Crop tonight is squishy likely from all the water it has been drinking. Will check it in the morning to make sure it empties to rule that out. I'm not seeing any other symptoms at this time.

I've separated it from the others this evening as it's every poop, just in case it's contagious. Little one was very displeased about that, so it's been hanging out with me tonight with a heating pad which seems to make it content, but can't do that all the time tomorrow.

Any idea what could be causing the green poop? Anything else I should try? Should I continue to isolate it (assuming yes until we know what is wrong)? Any tips on keeping it calm on it's own without me until we figure this out?

 

[Peachyfrog]

Update:

Poop seems to be improving on it's own with time, though not completely normal yet. Has been eating some feed, but not enough to fill it's crop, so been giving it some boiled egg couple times a day which it's been eating and filling it's crop the rest of the way with. Drinking normal amounts of water today.