I have 16 4 week old chicks. Four of them are bantam and the others are standard. I have a chick that I have (what I believe) to have pasty butt. (S)he has had it since day one. This little one is a silkie and when I check him/her her vent is white from her poo. We had some chicks that also were "sneezing" and "coughing". We changed the bedding from shredded paper to pine shavings. That seemed to clear them up right away. I think they might have had a reaction to the ink on the paper. At the same time I put poly vi sol (without iron) in the water and added yogurt (plain) to their food in the morning(every day). My chick still has white on her vent but may not be pasty butt. It doesn't seem at caked on as before. I just don't know how to clear this up. I've had people suggest apple cider vinegar to add to the water. What will that do? I had given our chicks the poly vi sol for about 2 weeks and same with the yogurt. Is that too long? Yesterday I changed their food from medicated mash to medicated crumbles. I want to do what is right for chicks. What do you suggest? Do I continue the poly vi sol? Yogurt?