After rigging a hand how do I make the fingers longer easily without messing anything up

I’ve got the hand rigged just how I like it to be

and I realized that the fingers on my mesh hand are too short. How could I increase the length of the fingers without messing anything up so I could animate quickly. Here is the blender file that I’m working with
any help would be appreciated

QUICK EDIT: the main part of the fingers that I’m interested in extending the length on is just…

…sorry I don’t know how to refer to it verbally but I circled it and posted it so if you could help me increase the lengths of just that part ideally on all four fingers at the same time because I’m an efficiency expert but anyway you could teach me how to do it I’d appreciate it!

EDIT 2: the way I rigged my hand I can’t even do a vertex slide on one vertices without completely decimating the entire mesh I can sculpt though…if there is a way you could tell me to get around that then I can edit the vertices in edit mode and accomplish my goals. Just for note…to make this hand I cut a hand off a makehuman character that I rigged and imported into blender.