Welcome!
For
@FeatheredFriends&Horses2 , and everyone on this thread; it would be best to actually look up what's approved organic, and what's not, before posting wrong information. The FARAD.org website has amprolium as an approved drug in the USA and the UK.
As a new chick owner, the safe plan is to feed the amprolium medicated feed, if you are in the USA.
And chicks can be vaccinated for different things! Marek's vaccine is a good idea, and amprolium is not relevant to that. Coccidiosis 'vaccine' is the issue with amprolium; one day on the medicated feed wipes out it's effectiveness.
Here we buy Marek's vaccinated chicks, and stopped feeding medicated chick starter, because of having years of no problems with coccidiosis. (Crossing fingers that one year this will no be a terrible idea!)
Our entire flock, chick to seniors, eats an all-flock diet, Flock Raiser, with separate oyster shell for the actively laying hens.
When you buy feed, look at the mill date on each bag!!! It should be within a month or six weeks, and used up within two or at most three months of that mill date, for best vitamins and freshness. Old feed is not a good thing!
Mary