The shrimp don't have a very large bioload, so I don't think that would be a problem, though I certainly wouldn't add any more fish.
When you said "2 female fighter fish" I assume you're referring to bettas? You didn't ask, but that's playing with fire. The females can be just as aggressive as the males, so it might not end well. Some people keep them in "sororities", with multiple females, but that's with more fish to spread out aggression in relatively large tanks with ample hiding places, and even then they don't always work.
I'm not saying to immediately separate them, but I'd strongly recommend keeping a close eye on them, and have a backup plan if they do become aggressive as they get older.