At 18 weeks I suspect they will all be laying any day now. Depends where you got them from, but my isa browns were only vaccinated for marecks. Cocci is in the soil and sometimes they'll get an overload on their system. You may as well source the product now, because if your going to keep chooks you'll need to have it in your first aid box. I would give them some plain Greek yoghurt for good measure. Good pro biotic to balance the gut.
