Son was 9lb at birth, 8lb 7 oz at 4 days old, 9lbs at 2 weeks 1 day, now 9lb 9 oz at 3 weeks 5 days. 8-10 wet / 6-8 dirty diapers a day. he was 80th percentile and now 53th percentile. why? normal or a sign of issue with exclusive breastfeeding?

After the 1st wk of life, after all babies lose weight (usually water weight), they begin to grow a long a particular % growth curve that is often not exactly the % of their birth weight. If your baby has re-attained birth weight in the 1st wk & is growing along the 53%, that's normal & means nutrition & hydration are adequate. Weigh at pediatrician's to make sure growth continues on that curve.