Sick Zebra Spiny Eel

Hey everyone, I joined this website to hopefully find a way to save my zebra spiny eel. I've had him for 2 years and I love him so much...
I have a 75 gallon freshwater tank with two 75 gallon filters. All parameters are correct. Inhabitants in the tank include the zebra spiny eel, 3 angelfish, and some scissortail tetras. The eel and the other fish eat thawed brine shrimp and blood worms (if necessary I plan on switching to live as my eel grows). The substrate is sand for my eel to burrow in and I have made sure that he has a lot of places to hide ever since he came into my life.
About 2 weeks ago, I noticed that he started breathing with his mouth open. Fearing injury and/or bacterial infection I began more frequent water changes with a daily dose of Melafix. A week into treatment, I noticed that he is breathing slower. I continue treatment but noticed that he has developed growths on his face that seem to be preventing him from closing his mouth and eating. He seems to try and grab the worms/shrimp but cannot get them in his mouth. I pray that he is eating when I am not looking. I cannot find out what is wrong nor how to treat it. Please help me save him, I love him dearly. I have attached a photo below that I just took tonight at feeding time.

More pictures and video required.

It should be full grown if it's 2 years old.

Stop adding Melafix
.
Wipe the inside of the glass down with a clean fish sponge.

Do a 75% water change and gravel clean the substrate. Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. Wash filter materials/ media in a bucket of tank water and re-use them. Tip the bucket of dirty water on the garden/ lawn.

Increase surface turbulence/ aeration when using medications because they reduce the dissolved oxygen in the water.

Add salt, (see directions below).

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SALT
You can add rock salt (often sold as aquarium salt), sea salt or swimming pool salt to the aquarium at the dose rate of 1 heaped tablespoon per 20 litres of water. If there is no improvement after 48 hours you can double that dose rate so there is 2 heaped tablespoons of salt per 20 litres.

If you only have livebearers (guppies, platies, swordtails, mollies), goldfish or rainbowfish in the tank you can double that dose rate, so you would add 2 heaped tablespoons per 20 litres and if there is no improvement after 48 hours, then increase it so there is a total of 4 heaped tablespoons of salt per 20 litres.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria but the higher dose rate (4 heaped tablespoons per 20 litres) will affect some plants and some snails. The lower dose rate will not affect plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.