Hi, wondered if anyone could help me. My little boy is 15 months old. Started to walk around 1 month ago confidently. I noticed tonight he has gone weak in the legs to the point he goes to the floor & then crawls & whenever he tries to get back up, he takes a few steps & ends up like jelly? I’ve only noticed this tonight. He has had Scarlett fever & still has it now & is on antibiotics. However , I am worried as to what this may be? He doesn’t seem in pain & is still a happy baby.