Blue cuckoo orpington with wobbly gait and toes curled up

[sixbabychicks14]

I'm hoping someone can help, bur my Orpington (about 4 months old) has started wobbling on his feet and seems to be stepping on his own feet. He is also off balance and his toes kind of turn up and shake a little. He just started this and we have no idea what it could be caused by. He is eating and drinking and picking his feathers but when he walks he kind of stumbles and wants to sit down. Any ideas? Thanks