Goldfish Scales Falling Off

[wendypizza]

Tank Size: 36g bowfront, with two additional goldfish not showing any symptoms

pH: 6.8 (the regular pH, per the LFS and my own tests, is 7.5)

Ammonia: 0

Nitrite: 0

Nitrate: 10

Hardness: 100

Alkalinity: 0-40 (usually around 40-100)

Temperature: 78

Right before bed I noticed my Oranda's scales are falling off. Panicked, dosed maracyn, 1tsp salt per 10 gallons, and added crushed coral. I'm not sure why the pH is so low; I've checked another tank and it's also 6.8, so I'm not sure if the water company is adding something to the water. I might wander to the LFS tomorrow and ask if they've noticed anything.

I haven't changed anything in the tank in the last week; on the 19th, I added some Fluval stratum and plants, as well as moved things around. Yesterday, I fed them rinsed, cooked carrots, Hikari Vibra-Bites and also brushed off some sand from this fish. I also topped off some of the water. Today I threw in some sinking pellets they've never eaten before. Other than those new foods, they've been eating the same food (Repashy, Xtreme) as they have been since I got them in September. I did not notice the missing scales when I was looking at the tank earlier today, nor when I fed them.

Is there anything else I can do for the fish? Or just wait and see?

(apologies for the lighting; the only light on that tank now is a purple grow light)

Edited December 28, 2020 by wendypizza
added temperature, details

[Colu]

It could have rub some scales off on something in the tank use  aquarium salt  and monitor if it get worse treat with maracyn

[wendypizza]

Replying to my own topic as the culprit and solution has been found--

The fish was wedging itself into the rockwork, presumably to get those morsels of food that fell in between the cracks. I found him stuck one day and rearranged the rocks, and he's healed pretty well in the intervening two weeks.

[Colu]

Good to hear he maid a full recovery