This may be just my imagination, but it seems that these tail feathers have appeared overnight. Does this change the opinion that this is a hen? It was hard to get a good picture. They are dark and pretty long. Chickens always know when you want a picture and they won't stand still!
Juvenile molting. They will go through several mini-molts in the first 4 months, and those molts can do some funky things to tail feathers. True male feathering doesn't even begin to develop until about 10 weeks old, and it can take weeks for those feathers to be clearly visible.