One of my week old speckled sussex chicks continually has a dirty bottom. I've been sticking her under some warm water to get the gunk off. It looks like normal poo, just stuck to her butt. All the chicks are on starter crumbles, and have plenty water and a heat lamp. What else can I do for it, other than keeping it clean? It's happy, eating, moving around, chirping- no other issues.