Making Bath Bombs?

I love making bath bombs and have made quite a few batches in the past month. Just recently I noticed that when my bath bomb is fizzing, there are a lot of little yellowish-whitish lumps showing. I have no idea what they are. They look really gross like warts. I'm thinking maybe it's the food colouring because I only made 2 batches with food colouring and both of them had this problem.

The other 2 batches I made were perfect! Also, I noticed that instead of floating on the water like they should, they sink down to the bottom of the tub! I really want to have my own soap and cosmetics business and sell at craft fairs and stuff so please reply! Thank you.

By Liv