Raising meat chickens

We are raising a batch of meat chickens for our own use.  We lost one of them about 2 days after we got them home.  That’s expected,  but 3 days ago we had one that seemed to go lame in one leg.  We know these things can happen if they gain weight too quickly.  We have been careful not to fed them too much so that they gain weight quickly and thought that we were doing a pretty good job of that.  we only feed them morning and evening.  They do not have food accessible all day long.

We brought that lame chicken into the house and were making certain it was getting food & water plus some extra Vitamin B shots & calcium.  He seemed to go downhill yesterday not interested in eating much or drinking much.  By the end of the day we thought he was not going to be alive in the morning.  He was still alive this morning but throughout the day it became clearly evident it was not going to live much longer.  He just died about an hour ago.

This is expected, but it makes us wonder what was wrong with him.