You could try posting in the emergency forums. There's some pretty helpful members on here. I usually wipe their bums until it stops. Sometimes it's because they are too warm or too cold, but I'm never sure which it is.
It's tough when you get a special needs chick. It separates the quitters from those who are willing to keep up the hobby, and find joy in it despite adversity.
Hopefully your little one improves as it matures. Sometimes they thrive after a bit, and sometimes they just can't. Probably due to an...