Children develop at their own pace
Don't rush children into developing before they have to.
Children develop differently. One thing I realised is never use a book to measure your child's development. It will drive you nuts and you'll always think there is something wrong.
My son only started walking a day before he turned 18 months but was speaking really well full sentences even. He is 3 now and still is a bit slow with physical movements. He still needs a bit of help up the stairs, etc but I think he is just a bit over cautious so we are working with him on his confidence.
We just need to carry on doing what we do. And if your gut tells you there is nothing wrong then nothing is wrong.