2nd fecal float test negative... Should be happy but I'm not

Just got the results of a second fecal float test... Negative. The first one was positive for roundworms (tomorrow they will get their second dose of valbazen).

Yet I'm still finding what looks kind like small pieces of raw hamburger in their poop once or twice a day.

I have a couple of questions and concerns that I hope someone will be able to answer, or at least venture a guess on.

1). If it's not worms or cocci, what else could be causing the intestinal lining hamburger looking stuff? Is there a test I can ask for to determine what it is?
2) should I stop the corid treatment now? They've been on the severe dose for 5 days, and today would start the 7 day light dose.
3). I heard a few sneezes this morning from one of my roosters. If he keeps sneezing, should I stop corid and start tylan?
4). I'm concerned about their gut bacteria. What food or supplements should I give them and when?
5). Some of them are molting so I've been mixing a can of cat food into their evening meal of ff/mash. Is that ok?

Thank you,
Debbie

 

Thanks ChickenCanoe, but what test should I ask for? I'm still seeing intestinal lining occasionally. I've got 33 chickens in the run and just this morning saw 3 or 4 spots of it. Maybe with that many chickens, it's not an unusual amount?

We are going on a two week vacation in a few days, and I've got 3 chickens with bumblefoot. I tried removing it, and was successful with one. The other two I couldn't get anything out of. One of those two now has a fever in the bad toe. Since my elderly mom will be tending my flock while we are gone, and I don't want her to have to deal with sick chickens, I'm thinking I should put the one with the fever down. Hate to do it because I like the little fella.. silkie mix roo I've had for 3 years.