Trees, Shrubs and Conifers: Oct. Red Maple question, 1 by Dennis_S

Dennis_S wrote:
I put 3 maples in about 2 years ago. 2 are doing fine but this one was not only a late starter but, as you can see, has only filled in the bottom third. I scratched the bare limbs and they show no green at all.

First, any suggestions why this would happen? All 3 get the same light, water, etc.
Second, should I prune back these dead branches? And is it best to wait till Fall/Winter?

Thanks in advance
Dennis