Pale fish w/ dark speckles on face. Dying

Yesterday I had to fish out my red tail shark that seemed healthy the day before. Today one of my tetras is showing similar symptoms.

The shark almost turned white (well light gray) and was just looking for places to hide, every once in a while it was start to float but catch itself and swim back down. After that, I upped the temperature did an emergency 50%ish water change and added more salt... My tetra is loosing color quickly and I can see some black discoloration on its head. Oh, when the shark died its eye (only one) was protruding, but not both, and was not that way until after... The tetra seems to have normal eyes.

Sorry for being choppy, I am trying to get everything.

Levels are as they have been for months. To be honest the only thing is I have not added anything in over a month, just a water change or two. I did notice some brown (maybe black even) algae now growing.

Other signs are disorientation and nose down swimming (if it does swim).

I tried to identify this on "that other site" but nothing seem to match up. Any help would be appreciated.

First, thanks for the help!!!

10 gal
PH: 7.8 - I can't seem to get this lower.
Ammonia: between 0 and 0.25
Nitrite: 0
nitrate: about 3-5
I have a liquid test and test before every water change.

I cycled this tank over the summer and since stocked modistly. I do water changes about every 1.5 weeks. No, not every week but more than twice a month. Lately (past 3ish months) everything has been fine. I did have an early fight with ick but clearned that up late summer.

This morning I noticed the tetra has a bit of a red eye. One thing I do remember changing is the time I feed them. Instead of 5pm I switched to 7-8am feedings. Could this be enough stress for the little guys?

These fish have been with the tank since or shortly after the cycle ended, I'd say about five months? Maybe more.

Sorry I was searching the forums here and found someone else with a link to a good site that has photos of illnesses. I don't remember.

"...and since stocked modistly."
2 tetras - one in question
3 neons
1 red tail shark - gone
1 "stingray" pleco
1 apple snail - small
30-40 mini snails - my wife likes them.

I have one lily plant. I do not add any chemicals except water conditioner after a water change, and salt.

As far as the ammonia being high, I tend to over estimate since the scale is a big jump from 0 - .25. The color is not exactly pale yellow but it is far from the .25 mark. Since the shark left, I changed the water that day, and will change again today (about 50% each change). That is every two days.

My wife got the tetras and I do not remember the exact name. They are deep orange with a black spot by the fins, black tail.

The neons are the standard neons, neon tetras I believe.

Roan Art: I am not disagreeing with anything you say, but years ago, I had a red tail shark in a 10 gal for about 6 years, then upped to a 29 for the remaining 4ish years he lived. Guess I got lucky with that one. The pleco is not even an inch long at this point, again you are far more knowledgeable then I with the waste it produces.

“and even not knowing what those other two are” I’m not following this statement. The tetras?

Thanks again.