Fish scales peeling off ?

[BoltonN]

Back again with some more questions about these troubled pristella tetras- one now looks as if it's scales have begun peeling off. There seems to be a creamy type colour of something in the area, it doesn't look like fungus, i'm unsure wether or not it's just the fish itself behind the scales but i have no idea

So far out of 13 of these, 2 have sadly died both with what seemed to be dropsy, one has recovered from the exact same symptoms and had the same treatment as the others in a hospital tank. The main tank has been treated with melafix and then esha 2000 3 weeks after the melafix. Water changes have been upped to between 35-50% twice a week. I'm really unsure as what to do now. Would this fish benefit from being quarantined and treated separately, it's seems to be swimming and eating well but the scales are worrying - none of the other 3 that have been ill have had this happen. Background = ph: 6.8 temp: 24.5 gh: 3-4 kh: 1-2. ammonia and nitrite both 0. nitrate 5. Sorry again for keep asking questions on the same fish

[plankton]

DOn't apologise.
It's sad you're having so many problems with this group of fish.
X-rays are usually pretty hardy, so this must be a particularly poor batch.
Can you get a pic of this fish, it would be helpful to see exactly what is going on?
Have you got any sharp things in the tank?

[Vale!]

This is just an observation in case it helps to diagnose what's going on : a fish's scales don't lie solely on top of its skin ; they originate from several layers down. So if scales are dropping off, it may be that the underlying tissue is being compromised.

[BoltonN]

These were the best pictures i could get, it does have w dark mark similar to the others who have been ill however it is swimming and eating well, in addition the others all seemed to have dropsy and this one doesn't have a swollen belly, the tank is mainly plants and plants be large piece of driftwood (doesn't have any sharp edges really it all got sanded and also there's some slate which is obviously normally sharp however i spent a good deal of time grinding down the edges and then sanding and all are smooth rounded corners (it's relatively thick aswell which helped get it smooth)

[BoltonN]

[plankton]

It does look like damage. Melafix will help prevent secondary infections while it repairs.
Is there anywhere it may have got caught at some time? It sounds like you've taken care of sharp edges.
(I would note that I won't use slate any more as, even though I made sure there were no sharp edges I still had fish get damaged - corys)

[BoltonN]

@plankton Do you feel like another fish may have been able to cause the damage? There is one much larger fish, also a pristella, and it can be a bit temperamental - especially during feeding.

[plankton]

Possibly, but I can't see another pristella doing that much damage before it got away.
It's more likely done it on something as it has got away.