I might need help

[Tvis]

So my aquarium is a few years old, and it was doing just fine until recently, so i bought a black molly, well over time the molly started to act odd got very skinny and died. Around that time my bushynose pleco got very territorial towards my corys to the point where the got very sick, i lost one so far, and im lost.

They have like a white slime around them, and flayed fins, also not eating, the one has its eyes sunken in, the bigger cory is showing signs of white dots that are very spread out.

The other fish are doing just fine.
5 cherry barbs
Opaline gourami
2 peppered corys (whats left)
A sa bumblebee catfish
And one tetra ( dont ask)

So ive been treating the tank with primafix melafix combo for about 3 weeks, it helped before so i thought why not. Well not really seeing any results.
So i figured it was ich ( ive had ich before and cured it)
So i applied that medication, nothing.
So i waited a week and maybe thought parasite buut idk.
Also its getting pretty cloudy.

I do a water change every week, its 36 gallons and very dense in the plants.

I have a oversized filter and a bubbler.
I tested the water and the parameters are where they are supposed to be.
I honestly believe the pleco caused all of this. I really could use some help

 

[Aiken Drum]

Can you post a photo of the infected fish?

Can you quarantine?

Could you explain more about why you think the pleco is the cause of the infection?

Also a bit about ich.

Ich can only be killed while its in the free swimming stage of its lifecycle. While a fish is visibly suffering from ich your treatment won't be effective, your fish will either survive or not once infected regardless of medication. The free swimming stage can be several weeks after the visible signs are gone, so if you stopped medication once your fish are no longer visibly affected the ich parasite still be in the tank waiting for an opportunity to reinfect the fish. This is why water temperature is important. At 30c the complete life cycle of the ich parasite is reduced from several weeks to 6 - 8 days and so medicating for a few days after the ich parasite has dropped off your fish at this temperature will have a better chance of catching the parasite while free swimming and killing it. Higher temperature also reduces the infection period and so recovery chances are greater. This might be why you seeing signs of ich again.

 

[Tvis]

So i do have a ten gallon but it has shrimp in it. The 2 corys passed over night. I think it is the pleco because of how aggressive its become causing stress for the corys.

The one cory had like a red patch behind its fin and what looked like a hole leading into the fish. Could be just the decay process. I buried the cory, i could dig it up. I took a picture a few days ago.

 

[Tvis]

I forgot to mention that i did have a panda cory

 

[Tvis]

Update i only have one cory now and the pleco chased my catfish out of cichlid hole he lives in

 

[Tvis]

I maybe should have sent the messages to you instead of the thread um oops

 

[Tvis]

Hello? Anyone still around?

 

[Aiken Drum]

Are you able to quarantine sick fish?

If you have fish thats bullying another fish the only real solution is to seperate them.

Do you know your water parameters?

 

[Tvis]

I could move the pleco to the ten gallon, parameters are
Ammonia 0
Nitrite 0
Nitrate 7
Ph 72