Hey Bill,
I know the Nitrites level you posted was 0 but that makes little sense if the tanks still cycling. I have a feeling you have or are having nitrite spikes. Salt may help with blocking further Nitrite uptake during cycle, but Methylene Blue should take care of any nitrites absorbed already. (kordon brand is at many petshops ..if not Jehmco.com should have the pure powder) I believe the fish will naturally work those out of their system in 2-4 days.
I would suggest bumping up the water to 80-90 % per day until symptoms resolve and check your nitrites kit for expiration. I'd also switch to Prime for now unless safe says it detoxes nitrites.
hth,
al