My son was not diagnosed has having low tone, but he was very slow to hold his head up, push up, crawl and walk.  I worried all the time, but his ped. would  say he was fine and he was!  Carter crawled at 11 months and walked at 14 months.  I also think he was slow because he almost died before he was diagnosed.   He was very sick for the first few weeks of his life.   

Carrie