Ok so I've been looking into cures for blackhead, i have found an old thread. metronidazole was suggested. Is an antibiotic. For humans you need a prescription, but they have it for animals which you can buy online.
For some reason I can't quote the post so I screenshot it:
It's from @casportpony
I believe Avian flu usually has green poop and usually see signs such as coughing, wheezing, and sneezing. In this case antibiotics might help.
I believe with E coli the only thing to be done is antibiotics and even then it might not help.
As far as dietary issues I'm gonna need a little time...