I had an impeller split like that before my tank move and I developed a few issues with my SPS as well, I think it would depend on how long it was like that. You could always try poly filters if you suspect some heavy metal leakage.
Rusting magnets are never good in a sps tank. It's been documented in quite a few systems that were having problems and the source being rusted magnets/ cheap stainless steel
Yea i'm thinking this might be one of the reasons. Just my sps and montis were taking a hit and receding. Didn't know why. Seems this has been leaching for quite a while. THe tube is swollen with complete rust.