Its pretty unlikely its the cories. Sand doesnt stick and makes the water cloudy, but its so fine, it also actually looks like sand...
My best guess is its the meds. If your done with the treatement, then get the cardon back in (provided its still fresh) and see if it clears it up. A similar tactick would to be to put in a load of fine filter wool or similar (if the silter doesnt already have it) at the start of the filter, this should get rid of anything floating in hte water of a period of a week or so.
But since the water conditions are ok, and providing the fish look happy, i wouldnt worry too much. It should settle down over a week or two as its cleaned out by the filter. I know it ruins the view tho...
hopefully someone else will have some more insight. all hte best.phil