White in infant stool

My son is currently 5 1/2 months old and very healthy. For the last week or so he has had white particles in his stool. They appear to be the same consistency of the rest of the stool. The white is seen throughout the entire stool. The color resembles a "dirty* white/light yellow/tan color. The rest of the stool is a regular brown/yellow color. The pieces of white are small in size (approximately 1/2 pea size). The are not mucousy at all, they appear dry. He also has begun to have some seedy stools again (he is in soy formula) He has tried no new foods that we can attribute to this change in bowel color. His frequency of stool has not changed nor or other factors in his diet or personality any different. I have read that light colored stools can be indicitive of hepititis (hepatitis) or bile obstruction, but I didn't know if the whole stool needed to be light colored or if these pieces suggest a potential problem. We called his pediatrician and he did not seem concerned. What could cause this change? Is it possible that his formula is not digesting fully? His urine has not changed at all. Thanks for any info you can provide!