Hello, this is Dr. Linda. I am sorry for the delay in responding to your question. I only just came online so I hope I can still be of help.
There are way too many reasons for Clyde's illness to try & diagnose him without a hand's on exam, but there are a few things you can do if a veterinary examination is out of the question.
The first thing is to deworm him. Valbazene (albendazole) is one of the best ones, but if Clyde has never been dewormed, you can also try SafeGuard (fenbendazole). Before deworming, bag up a sample of his stool & have your veterinarian do a fecal exam looking for other parasites, especially coccidia.
A dose of LA200 would not be a bad idea, start with a dose of 10 mg/kg ( approx. 2.2 ml/100pounds ) under the skin every 48-72 hours. Use your probiotic as labeled & consider using an electrolyte & energy drench such as BounceBack.
Make sure he is well bedded & out of any drafts. If you do not see any improvement in the next 48-72 hours, please contact your veterinarian. He may require more intensive treatment or medications than what is available in the feed stores.
I hope this makes sense & at least gives you a start in trying to help Clyde. He has already been sick for 5 days, so hopefully you can get him turned around.
Please let me know if you have any further questions or concerns.