I've kept chickens here for about four years now. Every year I get a few from the feed store and every year everything is fine... Til this year. I bought ten feed store chicks in April/may and about nine weeks ago I brought three home from a friends house. One vaccinated pullet and two chicks not vaccinated but hatched at her house under a broody. Anyway, yesterday my 17 week old silkie (from the feed store) who had been acting perfectly normal prior was sitting way out under the trees where they normally dust bathe when it was time to come in to the coop. I went over to get him and he didn't move. Actually some flies had started bugging him. He couldn't stand or walk. I brought him into the ac and gave him some water - had to hold it up to his beak, and some chick starter. Today he has the use of his legs but they are very weak. When he tries to stand he has to balance on a wing. Both feet are forward when he sits. His poo is normal, no diahrrea, and I see no ocular changes. I don't get it it happened so fast! My first thought was mareks but some one Also mentioned mold as its been very hot and humid here. Any thoughts?