dropping feathers

Today I noticed that one of my pullets (3.5 months old) has pieces missing from her tail feathers (picture included). I also found 4 large, healthy looking tail feathers lying in her coop. Her tail is noticeably less full than those of my other 3 pullets. The rest of her feathers look fine. I...

Is this even possible ? My gorgeous RIR 6 month old hen started suddenly dropping feathers today..she's healthy otherwise What's up? She takes a daily dust bath. She gets greens and a varied diet including laying mash and scratch too .. I'm so concerned.