You have two things going on here- The clowns have secondary lesions associated with brooklynella and the foxface has cryptocaryon which is Marine ich. Priority is to treat the marine ich. For the foxface, treat in a separate quarantine tank with coppersafe or Copper Power at therapeutic level 2.25-2.5 For a FULL 30 days (do not interrupt this 30 day period) monitored by a reliable Copper Test kit such as Hanna Brand- No API brand. Also monitor Ammonia levels while in quarantine with a reliable test kit and add aeration during treatment using an air stone.
The display tank will have to be kept fishless (FALLOW) for 6-8 weeks to assure the existing parasites go through their life cycle without a host fish and die off
For the clown, this mucus generally starts at the facial area as well as gills and spreads across the body producing lesions as it progresses often confused with ich and can turn into secondary bacteria. Other symptoms will be lethargic behavior, refusing to eat and heavy breathing from the mucus.
Typical treatment is a formalin solution is mixed with in a separate container with either fresh or saltwater. Start with a quick dip in the formalin at a higher concentration then performing treatment in a prolonged bath of formalin base at a lower concentration in a quarantine tank. The longer the fish are exposed to the formalin treatment the more effective it will be at eliminating this issue.
If a formalin solution is not available for immediate use, temporary relief can be achieved by giving the fish a FW bath or dip in water same temperature as display tank. Even though this treatment will not cure the disease, it can help to remove some of the parasites, as well as reduce the amount of mucus in the gills to assist with respiration problems.
Treatment is best done in a QT tank using either quick cure (more effective but now harder to find) or Ruby Rally Pro. Ruby takes a little longer and initial treatment generally takes 2-3 days to really start going to work.
With the advanced stage of this- I recommend immediate quarantine of all inhabitants and leaving display without fish for 4-6 weeks.
A quarantine tank can be as simple as a tank from a second hand store or a starter kit from Walmart which most of the needed essentials.