lathagic chick with eyes half shut

[Goldendoodles]

I have 5 3-4 week old Welsummer chicks that I just bought at a livestock auction last week end. I Am kicking myself now for not looking them all over better before purchasing. One chick has eye issues, she cann't seem to open her eyes all the way and tends to walk around with one or both shut completely. She sleeps all the time even when the others are all busy running around, but still eats and drinks normally. Does anyone know what is wrong or if she'll get better? I think I'm going to separate her just in case she has something that's contagious, it would be horrible if they all came down with some disease. Hopefully whatever it is will not get worse.
here's a pic of one eye, the other was closed at the time.

 

[purpletree23]

When you purchase new stock you always have to quarantine them for at least 1 month. Some do it for a shorter period of time but I like the month. You can separate her but it's probably too late. We have to figure out whats wrong with her so all of your chickens can be treated.

Is she coughing or sneezing or making funny sounds when she is breathing?
Is it warm enough in their coop? The night here have been chilly. Not warm enough for a 4 week old chick.

 

[Goldendoodles]

All the new chicks are living in my spare bathroom with a heat lamp thankfully far away from the rest of my flock. She doesn't appear to have any of those symptoms, but she isn't looking so good.

Her right eye is always shut now and she will only stand for a few moments before sinking down to sleep. I have her separated so she won't be bothered by the other chicks, but I don't know if she's gonna make it