No worries, I miss stuff all the time.
In the video you jsut posted, it appears as if the fish has some lymphocystis on the caudal fin, it could also be a fungal infection. Hard to say.
At any rate, my suggestions would be as follows:
Vacumn the sand bed to remove any possible cysts if there is a parasite. Lower the salinity to 1.012, and if you do not already have it mixing, get some saltwater mixing ASAP. Also, reduce the feedings for the next while, it sounds like your tank may still be cycling, so we want to reduce any nitrogen imput as much as is feasible. Adding more live rock may well help to jumpstart this process and hopefully remove some of the nitrite.
Also make sure that the damsels are not picking on the clownfish, stress is the last thing it needs at this point. The video you posted of the fish from a few weeks ago was much clearer than the one you posted showing the sickl fish, any chance you can try and get another video of the fish as it is now, hopefully a little clearer?
And again I would suggest some Methyl blue to help ease the nitrite burn, it will also help any fungal infections. I have used it withouy to much trouble with hermit crabs, but not promises.
The ideal situation would be a QT tank, is this possible? All you would need is a 5 or 10 gallon, heater and airstone.
Keep us updated.