yellow but with mucus

I have been dairy free for about 2 weeks now and I know it isnt completely out of my system but I have a question for you.

On saturday I had some Mcd’s french fried not realizing they had dairy in them. Well today he had mucus in his diaper. This was the first time I had seen it since I eliminated dairy. He only poops every other day so is it safe to assume that the mucus today was from Saturdays slip up?

I still havent cut soy b/c I didnt think I needed too. He is happy all the time and sleep is better but not great. ????