chickens

hi iam Sheila cheers, ive got a new batch of chicks now 4 months old,

feeding them the required feed and corn, they love bread.1 but they been hakeing a honking noise
is this normal or not they are different breads, buffs, ee's, long horns , jersey giants, ect.
and some having black stool. concerned.! I alove my 27 chickens. all girls but 2.