I'm sure you've already heard this advice, but I'd focus my efforts on water quality if I were in your position. Adding a cleanup crew is a decent idea, but it only takes care of the symptoms, not the actual "sickness." You need to ask some of the fundemental questions like... what's my bioload, how often and how much do I feed, are my water changes sufficent, do I need an RO/DI filter? If you keep following this logic you should eventually solve your problem. I won't lie, this can be a painful process and it's much less exciting than adding a bunch of interesting little creatures. Good luck!