I remember a tweet from Alex Valle once: “Protip: If you’re playing only one fighting game, you are limiting your potential.”
The thing is, I know how you feel. Especially if you’re busy with a job or school, you can definitely notice your execution slipping if you don’t constantly practice, and you may develop bad habits from certain games. I can’t tell you how long it took me to try to stop pushblocking in SSFIV when I came back to it after a while of only MvC3, and then the button-blocking of MK9 threw me off for way too long.
That said, take Alex’s ‘protip’ to heart. I also feel that some of the experiences I get in one fighting game often translate to another. You can learn clever ways to move around and mixup, you may learn a new way to execute certain motions that you never considered before, etc. And the “bad habits” I say you can develop, disappear over time, and then you can competently jump from one game to the next with ease.
I play multiple games. In fact, pretty much as many as possible. Along with the three you mentioned, I also play around with Melty Blood, Vampire Savior, and Guilty Gear. Sure, if I only played one game, I could be better at it, but I don’t think I would be MUCH better. If you enjoy all three games, play them all. You could, however, try focusing on only one game for a few weeks or so, and see if you like that better. If you find you miss playing the other games…then you found your answer right there through your own experiences.