My Baby Is 5 Months Old, Growing Steadily But In

My baby is 5 months old, growing steadily but in the 3rd percentile. She's 5.5 KG. Had her stool checked and has white and red blood cells in it. First doc said nothing was wrong, but the immunologist we went to wants to retest (6 weeks later we finally got the results- Thanks Australia!). I'm Solely Breastfeeding and it was recommended from 6 weeks+ for
Me to be dairy and soy free.. should I be concerned? Any recommendations?