You need to clean their little bottoms off, do so gently by using a warm wet paper towel, try not to pull it off as their skin is delicate and you could rip it or damage them. Once you get it off, dry them off well and keep them warm. Put a little ground corn meal in their food, that will help prevent pasty butt. Every time you give them new feed, put a small handful into the feeder and shake it up well.
You may want to go to TSC and see if they have eletrolyte powder to mix a little up in their water to give them a boost. Worse case if you can't get that, some sugar water would give them a boost too and extra calories.
As for their food, get some baby chick crumbles, the 16wk old stuff may be too much on their little systems. I always give my new chicks the medicated crumbles and they do very well, right now I have 9 four week old Ameraucana babies and they are doing very well on what I described above, with the exception that one is a runt, but even she is viable and hopping around.
Edited by CariLynn - 4/17/12 at 1:01pm