3 week old chick

[WALKER4388]

im new to this but one of my chicks is having diarrhea on and off and this morning the diarrhea was covering his back side so I cleaned it all off of him but I also noticed that he is much smaller then the rest of the flock , he is eating and drinking fine also he is running around fine he does have a few feathers that look to be missing any help would be greatly appreciated! thanks

 

[Hollywood Chickens]

Give him a little plain yogurt the probiotics often help with poo issue. What color is his poo?