I hatched three chicks from my flock. They are three weeks old. Today one of the chicks can hardly walk. It's leg is not sticking out like in straddle leg. It has been fine until now. The other two seem to be doing great. Is this a vitamin deficiency? One leg does not work well, but it can move it. Since these are from my own flock I am worried if it is a deficiency. Any advice?