I have the same thing going on with my six right now. And they are the same type too. What i found works best is to snip the little fuzzies with the poop stuck to them off. And if it is really bad, soak the chicks bum in some warm water then put some oil on its butt (you can even use vegie oil) and fix them some boiled eggs to harden up their poo and also some plain yogurt if you have some. After a few hours check the chicks again and then apply and thicker oil (like vaseline or Neosporin) and your chicks will be fine! Give them love and cuddles, them being small i think makes them more lovie and cuddly and love can heal anything!