This is what I do:Yeah, it is!
I got a bottle of the liquid from a neighbor who also keeps chickens (a few months ago when I had other chicks with Cocci).
I bought a packet of the powder yesterday. I haven't had a chance to read the instructions, as I haven't had need of it (I still have the water I made up with the liquid my neighbor gave me). If you have a link or something, the product I have is the 20% powder (amprolium).
Corid Dosage:
If any show symptoms, all chicks should be treated. There is 9 species of this disease and ONLY 2 that have blood in the stool. Critical time is when chicks are between 4-16wks. of age.
chicks need to be treated when they are 3-4wks of age. 20% CORID POWDER....1.5TSP. PER GALLON FOR 5 DAYS and then another 5 days at 1/2 tps per gallon.
and to repeat it every 3wks if they have symptoms until they reach 9mos. of age.
After this its a good idea to put it once a week in their water.
Since you are losing them and the corid helped, I would follow this for the current year. It might be better next hatching season.