The increase in nitrates again indicates your donated media is doing their job.
Salt and cories is a bad mix. Personally, I wouldn't do it. Cories are very sensitive to that, watch for ANY signs of stress from them. If they shows stress, do a PWC (regardless of what the Stability folks say) and SLOWLY add non-salted dechlorinated water back. You want to do this slowly, as the salt concentrations change, it can cause issues for the fish, especially the cories. Take your time filling it back up. If you are using a hose, a very slow trickle back in. If you are using buckets, a cup at a time. Patience, IMHO, has never hurt a fishkeeper or their fish.
Salt and cories is a bad mix. Personally, I wouldn't do it. Cories are very sensitive to that, watch for ANY signs of stress from them. If they shows stress, do a PWC (regardless of what the Stability folks say) and SLOWLY add non-salted dechlorinated water back. You want to do this slowly, as the salt concentrations change, it can cause issues for the fish, especially the cories. Take your time filling it back up. If you are using a hose, a very slow trickle back in. If you are using buckets, a cup at a time. Patience, IMHO, has never hurt a fishkeeper or their fish.