I’ve heard about lettuce causing diarrhoea actually. Maybe cut down on the greens & treats and see if that helps?
Did you do a follow up worming treatment two weeks after the initial dose? If you don’t regularly worm your flock, a repeat dose may be necessary.
The conditions that favour worms...
I don’t know enough about fermented feed to comment unfortunately but an additional probiotic won’t hurt.
I wonder if the inconsistent weather is affecting your chooks. Some can find it harder than others. How long has the diarrhoea been going on for?
I would try a probiotic over anything else. Do you have weather spikes where you are? Do you notice the three in question drinking more? Excessive thirst can indicate issues with the kidneys. Make sure they always have access to proper sized grit and flaked oyster shell.
I would probably trim...