Seen this before mate, I put it down to Paratyphoid. Birds go down on their legs and cant even get of the floor with wings spread. I seen it in 2007 when i did the birds with paratyphoid injection and soon after Paramixo injection, nearly wiped me out. Baytril will bring the birds round but it will be slower second time round and some birds will perish. Best to get checked by a vet who knows what they are talking about.