Okay so my daughter is 7.5 months and does not crawl, does not pull herself up, does not hold onto me with her hands when I hold her on my hip and cannot stay in a push up position but she can do everything else like sit up, scoot, bounce, support her weight on her legs,ect. My mom pointed all this out and said she is concerned that her arms are weak?? Should I be concerned?? What should she be able to do physically??