Sick turkeys need help

[IdahoPrepper]

I do not know what I am doing wrong. Will post facts so far.

1 of 3 turkeys was laying down with head tucked.
Tried dewormer but bird died next day.
Poop was egg yolk yellow diahrea.
Looked up symptoms, said blackhead.
Bought all-cure from fish store.
Treated 1 packet per bird (12lbs-15lbs) orally with shringe per day.
Poop got solid on two birds left.
Stopped after 5 days.
4 day later, after stopping, dark brown gravy type diahrea one bird.
Treated again for 5 days and poop got hard again after 2 days like before.
4 days later brown wattery diahrea again, both birds.
Treated for cocci, as that can have yellow poop as well, I read.
Birds got sicker after 2 days, not eating or drinking, not moving around, heads down, wings dropped one bird.
Just started treating metranidizole (20% powder) 1/2 tsp split by half for both birds. Rough estimate is 1.25grams per bird per day.

UPDATE: 12hrs since treating, one turkey has firm, normal poop, the other doesnt look good, laying down, eyes closed, head tucked, wings drooping.

What am I doing wrong? Why are they getting sick 4 days after
stopping medicine?
Medicines on hand, metranidizole, Baytril, Corrid, Ivermectin, Dectomax (we have a hobby farm).

 

[oldhenlikesdogs]

Are their heads getting dark? I don't think there's a good cure for blackhead if that's what it is.

Are they thin? Can you feel the breast bone?

Do you have mosquitoes where you are at? West Nile and other mosquito borne illnesses are more prevalent in fall. Also if you are wet where you are at cocidiosis would come to mind. How old are these turkeys?