Some organic debris is a good thing, exactly what the cup is for, but full of debris sounds like a recipe for rot so I'd probably dump and give a good rinse. City water varies. My municipal water is too mineral rich (leaves behind visible salts after evaporating) and I know there's a good deal of chlorine and fluoride added so I run it through filters and let it stand overnight.

As for the orchid mix it really depends on the bromeliad. I've had no issues using the bark-type orchid mix on my epiphytic and lithophytic bromeliads (Aechmeas and Neoregelias in my case) but I imagine it would be a somewhat quick death for a terrestrial bromeliad that has roots made for taking up water and nutrients. Do you have pictures or an ID on these guys?

flush the plants routinely and they will be fine unless you have toxic water.