Chicken feed, medicated or not can make them very sick. The rumen gets all out of balance pH wise and can be a challenge to treat, their rumen goes acidic and you need to buffer that with doses baking soda, magnalax, or any other product designed to buffer an acidic gut. But it is large amount you need to administer. My vet said to think of their rumen as a 5 gallon bucket and visualize how much that can hold and what you have to give to make a change in that much liquid. Of course you can do it gradually, but you are shooting for 1/2 c. of baking soda or 1/2 lb magnalax in 2-4 quarts of electrolyte (no sugar) every day for 3 or 4 days. Or a large bottle of pepto every day for 3 or 4 days. Also treat with Pen G, Probiotics, and Banamine.
Of course they may not be what is ailing your boy at all. I hope he continues to improve. Goats can be a challenge at times.