I'm new to pen spinning, I just finished the fingerpass foward which took me a few days to get. Working on thumbaround now which I find impossible.

Anyways, I'm left handed, when I hold my hand up and bend my middle finger down, my ring finger goes down with it. Every other finger I can bend down independently. Same problem is on my right hand, but with the pinkie and ring finger.

Will this affect any tricks? I know it makes it impossible for me to do the fingerpass reverse, but are there any exercises to get rid of the problem?

um, just practice bending the ring down while keeping the middle tense, practice will give it independence

You could do some Xtreme Digits, they really helped my fingers a lot. There are different exercises but you don't have to do them all. Put you fingers straight up and touching, then bend each finger, you will get better at it, but you need to concentrate really hard on which finger you are trying to bend and which you are trying to keep up. You will gradually get faster, it's a problem that can easily be fixed with a bit of practice.