First of all, I could be wrong, but I think the tank is a bit over-crowded. Really, the Rams should be in that sized tank on their own as far as I know. If I remember rightly, both the gourami and the rams (especially the rams) are territorial. If this is the case, the "finrot" might not be finrot at all - but bite tears caused by territorial disputes.
Secondly, unless otherwise stated, no meds should be mixed. I know from bitter experience it's a catch 22 situation. Do you treat for WS, or finrot? Treat and save one fish - or save them all from a parasite which could kill them?
I think my advice would be to quarantine the ram with a torn tail, and start treating the display tank for WS. Catch it early enough and you'll save yourself a job later. Run carbon in the filter for 2 days, and carry out a 25% water change. LHG, the disease advisor, might disagree with that, but that's what I would do.
You can use sea salt or rock salt from the supermarket but check the ingredients for any anti-caking agents. Table salt is definitely a no-no as Goldnugget said as it always has anti-caking agent and possibly other gubbins in it