My chick isn't gaining weight

[Sleek28]

She just had a really watery green poop. I’m not sure that’s normal...

 

[PDXJULES]

I have an Exchequer Leghorn (who came with a nick in her beak) was very assertive and pecking at eyes too obsessively last week. A bout with log-butt subdued her and seemed to change her behavior (the vent not pasted shut, but poo stuck to feathers below and built up). This week others have gotten rowdy, and she keeps away from them. Her body is half the size of the other 7 in the Brooder. She seems depressed and has accepted runt chick status, and doesn't eat or drink much...but loves bits of egg. She sleeps a lot the past few days, so I'm assuming she caught a bug - and all the others will develop immunity also due to her illness. She burrows to the middle of a group, then tries to stand over the others the entire time they nap. Wings seem to be getting long without body growth to support them. I'll scramble more egg and try to see that she gets more of it before the other crazies grab it all. Any ideas are appreciated. ( I didn't vaccinate, and have introduced a new branch every few days for gradual outdoor immunity). They get a good Chick Starter feed, Electrolyte water and occaisional Probiotic gel, that was sent from Meyer Hatchery, and a bit of teeny grit if any garden greens or egg are offered. Poo gets scooped often each day, and I watch temps closely.