My 18 week old Wyandottes have undergone a personality change. They've never been the friendliest birds, but a week or so ago they decided that they are terrified of me and everything else. They stay behind their small coop or in it and won't venture out much - they used to greet me if I came into the pen but now they come close reluctantly and don't trust any treats I bring. They don't even seem to like each other much. No eggs yet; only one has a comb that's turning red. What's up with these girls? The coop is a small pre-fab but they have a nice 18'x30' fenced pen (that is not covered). No sign of hawks, crows, etc. Any explanations for a 16-17 week personality change?