platy no slime coat

Question
QUESTION: I have a male platy who has been ill for 5 to 6 weeks now.  Previously, he was vibrantly healthy and the king of the platys.  He stopped eating for about 3 weeks.  He seems to have completely lost his slime coat (visually - haven't touched him).  He searches for food at each feeding, but he just continually spits the food back out.  He has lost weight dramatically - looks anorexic.  Still active, swims with the other platys, etc.  Have salt in the tank - 1 Tbls per 5 gallons.  Also Coppersafe 1 tsp per 4 gallons.  Tried Melafix for a couple weeks.  Also fed Anti-Bacteria Medicated fish food for a week.  After this fish finally tried miniscule bites of the medicated food, he finally began eating other tiny bits of food as well.  But a week later, he still don't eat enough and still looks 'dry' instead of shiny like he should.  Any ideas on what is causing this, how to treat or how to restore his slime coat?

ANSWER: Hi Sherri,
Sorry to hear about your platy. First thing I would do if I were you is a 25% water change. Then keep doing 25% water changes daily for about a week. Keep adding salt. If he doesn't look any better after a week, raise the temp a few degrees very slowly, and repeat. Keep an eye on your ammonia, nitrate/nitrite and pH levels and make sure your ammonia and n/n are all at 0, and your pH should be no lower than 6.8, if these aren't what your water is reading then you need to do some gravel vacuuming and possibly change out the cartridge in your filter. Hopefully that should do it.

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QUESTION: I don't think it's a water quality issue.  pH is 7.4 to 7.6.  Ammonia is 0, nitrite 0 and nitrate is 0 to trace.  I change 50% water weekly and vacuum the gravel each time. I maintain the salt ratio. Change the filter twice a month.  Temp is 80 to 82.  There are 3 other platys who are healthy.  Also a Betta, 2 Corys, 2 Mollys and a Cardinal Neon, all healthy.  Any other ideas?

Answer
Hi Sherri,
It seems as though this may be something I am not completely familiar with, since most problems I help people with have much to do with poor water quality. The only other thing I can think of is he somehow got a bacterial infection or even internal parasites. Parasites may be more likely since you have already tried anti-bacterial food.
I think moving him to another tank is a great idea only I'd reduce the water level to about 30% (depending on the size of the separate tank and filtration requirements). I'm hoping with some medication, it will help him and if you can take the stress of the water load off him, he may improve.
I had a similar problem once and it deteriorated to a point where his fins were starting to fray also so I rehoused him in the qt with a low water level and some broad spectrum antibiotics and funnily enough it helped my little guy.
As a side note, you will find that you can use a synthetic slime coat to replace his missing one by using Stress Coat. Salt doesn't always quite do the job.

P.S. If it is simply stress, it is very possible he is lonely. Platies usually do much better in groups of ten.