Hi Isabel. His growth is fine. At some stage they do slow down in their weight gain or otherwise we would all have baby huey's LOL. Plus he's on the go now and burning up more calories and also he's too excited to eat sort of thing kwim? There is just so much for them to explore and eating can sometimes come second to everything else. he still has had some excellent growth in length for that month though and you may find that he makes up for it this month too. If he is otherwise fine, and is well then I wouldn't be worrying about it too much.