chronic diahhrea

I have a not quite 2 yr old Marans who has had chronic diahhrea since I got her last spring. Other than that, she seemed normal but she only layed about a dozen eggs and then stopped completely.I have wormed her twice and recently treated her with Corrid for 3 days and then another 5 days. This seems to help a little but not much. Over the course of the last year she has wasted away to nothing. I know this sounds terrible to let her get like this but she is not a chicken who likes to be held and her outward appearance looked fine except for the wet butt feathers. It was only when she couldn't jump up to her roost that I picked her up and couldn't believe how skinny she was. Since her last treatment of Corrid her appetite has improved greatly and I think she is gaining weight. I have 14 chickens and she is the only one who has this condition. Does anyone have any ideas what this might be and can you give a chicken Kaopectate and in what dosage. Since she seems to be holding her own and even doing better I would like to give her the best chance I can. I don't have the money for a vet and she doesn't seem to be in any discomfort at all. The only reason I started Corrid is because I read that there is one variety of Cocci that can cause wasting but is not considered extremely pathogenic. Her diahhrea never had blood, just was always watery with undigested grains and cracked corn. Sorry to be so long winded. Any thoughts on this would be greatly appreciated.

 

She has never been a real hearty bird but she never seemed sick except for the persistent diahhrea. Then one day I saw her try to jump up 2 ft to her roost and she couldn't. When I picked her up she was skin and bones. Her breast bone had no meat around it. I will look up symptoms of avian tuberculosis. Never heard of it. I will start to put probiotics in her food too as Two crows suggested. I have human probiotic pills that I can grind into a powder at sprinkle of her food. Thanks for the suggestions.