I am not very experienced with chickens but it sounds like it could be molting or feather picking. Have you seen any of your chickens picking on each other? I know some people's chickens are molting already also.
I also had some feather loss recently and it turned out to be from lice, so...
I think mine got their coloring in around 3 months as well. By 4 months they had their coloring anyway. My hens looked like your second picture at that age.
I have 3 hatchery GLW pullets that I got from a local 4-H club. They are about 4 months old. This is my prettiest and calmest one, Nacho:
I think her lacing is so pretty! She doesn't have that nice fan shaped tail, though. Is that something that will show up later or will she never...
Here's my 4 week old GLW chicks! They are super sweet & friendly. I am thinking one might be a cockerel so I will post in the breed & gender forum too. Probably too soon to tell but one has a larger comb than the others.
Fluffy & Nacho
Sweetpea (suspected cockerel)
Fluffy...