In my opinion it is E-coli and will turn more liquid and smell very bad in a few days. I've used Nuflor shots on them and it did fix them up by the second shot. Also a product called Diaque which is a source of energy and electroyles and it will tighten up the feces put in the bottle of milk twice a day for a few days.
But it could be any type of bacteria which will cause scours. White usually is the start of some type of scours.