White runny poo

Got back from work at 3.30 and checked on the girls and did the usual poo pick round the garden and noticed 2 white runny poos. One had what looked like undigested pellets in it.  There where also a few flat ones about the size of a ten pence piece.  Have checked the poo site and am really worried as the pic that looks the same said poss kidney problems. Dont know which chick is doing it.  They all seem healthy and perky (even the one that is still a bit broody). Grace seems very skinny - she was the first to go broody - but laid an egg today.  They were wormed just before I got them 2 months ago.  Am really hoping the poos were left by a seagull as we have masses round here but dont think so. 
Jinty 

Thanks magicaltoad1.  Wll try not to worry and keep an eye on them.  It's hard not to freak out when you love them so much.   
Jinty