It sounds very similar to Billy's situation, overcrowded loft with well over 100 birds in a 12x6x6 loft, only ventalation was through the traps and open door.
They were never given anything but basis food, crushed sand stone and plain water all the birds were in great condition, apart from the lame pets all have been rehomed and members that have got them said they are still in great condition, I tossed 25 of the ones he intended keeping regularily in all directions and only lost four, the other 19 being rehomed to a restarter in Forfar, two whites were kept by Chickadee :-/