[Ember Tetra Skinny and Swimming Weirdly]

I have had them for about over a year. No new fish. Its not breathing rapidly its just swimming oddly. Kinda half upright, looks pale and wont eat. Havent seen any surface flashing.

[Ember Tetra Skinny and Swimming Weirdly]

I noticed this morning one of my ember tetras was swimming weirdly. I have a 29 gallon planted tank with some other common community fish. I noticed it was skinny and looked pale. I isolated it in a breeder box and put in a small amount of aquarium salt. It stopped swimming in the box for a second and almost go to the bottom before swimming again. What should I do and what is it. I have aquarium salt and the med trio on hand. 

Parameters

0ppm Ammonia and Nitrite

15-20ppm Nitrate 

100ppm Hardness GH

100ppm Buffer KH

7.8 pH

0ppm Chlorine

[Weird Anubias leaf]

What is this weird leaf coming from my anubias barteri

[Fish Not Making It Past Quarantine]

7.6 and 78-80 degrees.

[Fish Not Making It Past Quarantine]

I have a 10 gallon quarantine tank with a heater, seeded sponge filter, and some silk plants. I just got a school of cardinal tetras and I put them in the tank. They all looked healthy at the store and no signs of disease. I dosed the med trio for preventive measures like Cory says. I have also tried dosing salt with no luck. They all die off one by one per day. Water is fine with 0 ammonia and nitrite and 10ppm nitrate 78 degrees. Why do my fish not make it past quarantine?

[Cardinal Tetra died]

I bought a school of 10 cardinal tetras for my planted tank. 3 days later one of them died, parameters are all fine, 0ppm ammonia and nitrite, 10-20ppm nitrate. What could be the cause of the death?