Yeah it's always a good idea to get your blood levels drawn if you're on Tobi and you're having ringing in the ears no matter if you're having hemoptysis or not.
(Aminoglycoside, can cause hearing loss, ringing is a big indicators blah blah blah). I've found that UPenn (and by association Presby) is not really aggressive with treatment (at all, I'm at the point where I'm looking around for different centers because i'm so unhappy with them). So definitely keep on them and don't let them say something like this isn't necessary.