10 years raising chicks, never used medicated, although I do get mareks vacine, never had a problem.
imho, don't use it. you might need it if you have hundreds and hundreds of chicks in a poultry shed and can't keep things clean and cage your chicks. in a backyard flock? no.
same thing with antibacterial soap - hey, soap and water works great, and no reason to build up resistance to antibiotics in you or your chicks!