No, you do not always see worms in the poo, unless you are looking at every poo that each chickens has all day long. And the more chickens you have or bring in the higher the risk...And lets face it... chickens eat worms, wither they pooed them out or not. The only true way to tell is to have a fecal run at a vets. Wazine only treats round worms...... if they have some other type, it will not work. Most wormers that we use on chickens are made for larger livestock, Safeguard, Valbazen, Ivomec... etc... because most wormers for chickens are concerned with eggs and meat contamination to the public. I would put him in his own space, give him reg feed only and water and perhaps worm him and see if their is an improvement... that is the cheapest route. If you don't want to guess then a vet visit in called for. But many of us here have hundreds of chickens and we are telling you are best idea from what we know and what has worked for us.