Betta fish exhibiting illness

Two days ago I noticed my betta fish laying on the substrate thinking he was dead but I noticed he was still moving his gills rather slow. As I'm watching him more he would suddenly look dead and lay there then dart around the tank rubbing his face against anything he can reach. He's been mainly on the substrate and will have trouble swimming up to get air. I don't know what happened since he was just fine a few days ago. I do have a dalmatian molly (I'm getting more and possibly putting them in a different tank after quarantining the others) that was quarantined before I placed her in there with him in Oct. I'm not sure what to get to treat him if it's swim bladder disease.

The tank is 15 gallons
Water parameters are zero nitrites and ammonia, 5ppm nitrates, ph is 7.0- 7.6 water temps are 78 degrees. Also have a air pump in there.

 

Does his poop look long and stringy? There's a chance it might be parasites. Aquarium salt usually takes care of those.
How is his appetite? Is he losing weight?
Can you post a picture of him? There maybe some slight thing that will help diagnose what's wrong

 

Does his poop look long and stringy? There's a chance it might be parasites. Aquarium salt usually takes care of those.
How is his appetite? Is he losing weight?
Can you post a picture of him? There maybe some slight thing that will help diagnose what's wrong.

It's in the middle of looking normal and stringy. I did buy aquarium salt just in case of an issue so I've been doing that but not really seeing results. He'll eat if I tong feed him a pellet or pea and he looks the same so no he hasn't been losing weight.

Here is what I managed to take. His tail fins have been getting worse but I'm not sure if it's just from constantly laying/rubbing himself on the substrate or fin rot. The little bump towards the end has been there when I got him three months ago. I can tell he wants to swim since he excitedly moves his fins when I come up to check on him.

 

I'm wondering if that bump is a tumor and that's what is causing the issues.
It's not unheard of since bettas are often inbred for their colours/long fins. My first betta had a tumor on his face.

 

I'm wondering if that bump is a tumor and that's what is causing the issues.
It's not unheard of since bettas are often inbred for their colours/long fins. My first betta had a tumor on his face.

Yeah I read that too but it's unlikely since it's been months since he had that and he's only started acting sick about four days ago. The salt is kind of doing something since he managed to stay afloat in the middle of the tank to be fed instead of me having to stick my arm half way into the tank to reach him to feed him a pea

 

Try some daphnia, it works better for carnivores than peas.
Good luck