I HAVE 28 CHICKS THAT WE BOUGHT FROM MCM. THEY ARE 8 WEEKS OLD NOW. SINCE THEY ARRIVED, WE HAVE LOST 1 OR 2 A WEEK. THEY ARE FINE 1 MINUTE & DEAD THE NEXT. ALL SEEM TO HAVE A SWOLLEN BUM, VERY RED. SOME OF THEM GET REAL PASTY AND NEED CLEANING. WHAT DO I NEED TO DO? WE HAVE RAISED ABOUT 75...