Is my hen poorly?

Oh dear, I've only had my girls for a a week and one seems poorly. She's a warren, POL but her comb is still immature and pale. I have 2 warrens and 2 rhode rocks.

She's very timid, last out of the coop and last back in. She just mopes around and pecks half heartedly at food. She seems to be drinking more than the others. The other 3 strut around and scratch as if they've been here for years. This one just seems to isolate herself. Sometimes she's hunched, other times just gazes round aimlessly and seems generally disinterested in anything. She often stands in the corner with her back to everyone.

I looked at her crop this morning and it was slightly distended, but not nearly as much as the others when they go to bed. But then if she isn't eating much there can't be much in there! I haven't felt it - don't want to stress her by trying to catch her.

Am I worrying unnecessarily? How long does it normally take to settle in? Am I just comparing her with the others who have settled down so quickly? Any thoughts as to what I should do - I'm really new to this.

Thanks a lot. BG