Nothing wrong with it, but it seems like you are obsessing over some of these girls, according to what your posts indicate.
The question is, how many of these female friends do you actually consider only friends?
I hang out with like 7 females my age at school in this big group, but I only had a crush on one and dated another one. One of 3 males.
And, older or younger? Nah, that's fine. One female I know is 18, the other 19, and also the 19 year old was even my ex. Age doesn't matter as much to me, it's just you seem to have a crush on a lot of these girls.
Nothing wrong with that either man, but it's a good idea to just cool-off a little. Relax, y'know?
Just contuinue being freinds with these girls, and if something is meant to happen, then it will.