Sharon,
Nat was like this too, LS for a few days. Bought her to GP, he gave the "good bateria", mix in water for her to drink. Was better after 3 packets but now as n when, will still LS once or twice..
My guess is also teething..my mil taught me to see the LS, if its like flowery, then its due to teething...one day she poo liao, i peep into the potty, its indeed flowery leh..hahahahaha
Nat is poo potty trained...hahaha..will let her sit on the potty after her meals and "Nggggggg", usually she will poo de...
My mum is trying to toilet train her, no diapers during day time and will bring her to "she she" every now n then and training her to indicate if she wana sheshe..
So you continue to monitor him bah, should be no problem de...