My 6 month old baby girl put on 100g from her 4 month weight. She fell from above 50th percentile to 25th percentile. She is fully breastfed latching on demand. Should I be worried?

Cool! She is growing longer/taller. Now I feel more assured. Other than that she was indeed recovering from a bout of fever and cough when the measurement was taken. She is also very active - crawling and trying to stand all the time. Maybe that plays a part too.