Tire Track Eel Sick, Please Help

Hi TFF, I was hoping to get some advice/diagnosis about my poor tire track eel Sheldon. This morning i went in to feed him like normal but he didn't come out. He NEVER says no to a meal. And when i got my baster and put the worms in his cave he was kind of dragging himself and slowly eating them one by one. Usually when he eats it's like a shark feeding frenzy but he didn't seem to have any energy. A little while later he came out of the cave to go to his usual hangout (behind the cave) i noticed he had a big white patch on his tail. I've been (and still am) researching it but so far i haven't seen too much. His symptoms are he's really sluggish and he has the white spot on his tail. He's not breathing heavy or anything. Any help is appreciated. I'd hate to lose him just a few weeks before he gets his 200gal tank

Tank size: 26gal Bow front (temp, upgrading to 200+ gal after i move)
pH: 7
ammonia: 0ppm
nitrite: 0ppm
nitrate: 10ppm
kH: (need to get tester)
gH: (need to get tester)
tank temp: 79f


Volume and Frequency of water changes: 5gal (about 20%) once per week

Chemical Additives or Media in your tank: Canister Filter, 1 tray coarse/medium/fine mechanical filtering, 1 tray seachem matrix, 1 tray biohome ultimate (no additional chemicals)

Tank inhabitants: 1 Tire Track eel, 1 Common Pleco, 6x Tetra, 3x Danio

Recent additions to your tank (living or decoration): None

Exposure to chemicals: None
 
Sorry I don't have more photos right now. I'm waiting for my chance to snap more but he's hiding and i don't really want to disturb him if i don't have to. 
Thanks in advance!!

Photos will be a huge help in diagnosis, they will also help keep track of any further developments with the infection/ injury.

Could the pleco have decided for some reason to suction onto the eel and the resulting white spot and possible bruising is causing the sluggish behaviour and reluctance to move. Another possibility is that the eel has leant against a heater and caused themselves a burn, but usually fish are very quick to realise a heater is hot and wont stay near one too warm for long.

Thanks for the reply Baccus. I think it's a scrape judging from some other pics i've seen today. He got scared yesterday while i was cleaning the tank and he dug himself under an air stone and i'm thinking that could have done it. He doesn't seem to be breathing heavy like a lot of the infection stories i've read but he is a lot less active. I'll keep researching and i'll try to get some more pics posted. Any other eel owners have some advice/experience with this? Thanks again!

Hi again everyone. Im happy to announce that after some rest and a few days in quarantine he seems to be doing alot better. this morning he swam to the top of the water for food as he normally does. The white marks are still there but he's slowly been becoming more active the last couple days. I still hope that any spiny eel owners out there will chip in with their experience though. thanks again

Glad to hear he seems to be on the mend , maybe it was just a relatively simple injury he has sustained and not terrible disease.

Hey again. I finally got a good close up. As I said a few days ago I'm almost completely sure that it's a bad scrape and not a disease/infection. thoughts? Is there anything I can do to help him heal better? He's alot more active and fully comes out for food again. Is there anything that i can add to help him heal/feel better? If so do i need to move him back to quarantine again to use it? Thanks everyone!

Being an eel I would be very careful of most medications, but I don't think Indian Almond leaves being added to the tank would hurt. These have antibacterial qualities and can be very good for almost all aquatic creatures.