pale comb, ruffled dull feathers, low appitaie, sparating from the res

I recently i moved into a new apt, and took over the past tennants hens...
theres 5 all together, and have been great till like a week ago...
I think they are around a year and a half, and eat crumbles, scratch, and have access to our huge lawn..
we live in hawaii...
recently one of the hens...for a week now, has been acting strangely..
her comb is flat, almost over her eye, and super pale, her feathers are dull and fluffed up,
and shes separating hersel from the rest of the hens...i also have seen some feathers pulled out behind her neck, possibly from other birds...
as for her poo, havent really seen it besides whats clingying to her feathers...seems runny and white..
her eyes are a bit dull too...shes moving slow...
I was gonna let nature take its course, but dont wanna infect the other hens in the coop if she has a disease...
any tips?
I have looked through other posts, but dont have too much computer time...
mahalo for any leads