[Pineconing and white fuzz on Betta head and gill]

My male Betta fish has been acting a bit lethargic since yesterday. This morning I noticed he has a bit of white fuzz on the left side of his face and left gill. I treated with Maracyn Oxy but I don't know if that was the right call. What do you guys think?

[What is this fluffy stuff on the walls of my Betta tank? It's so creepy it's making my skin crawl.]

This is a close up of one.

[What is this fluffy stuff on the walls of my Betta tank? It's so creepy it's making my skin crawl.]

Some of the fluff balls have red dots in the middle of them. They flow in the current but don't seem to detach and it seems like there are more of them every day. This tank is no more than 2 months old. There are 2 species of snail in it as well; assassin and bladder I believe. 

[This angelfish I was treating for fungus(?) died after an ammonia spike.]

• pH 7.5
• Nitrates 0
• Hardness 100
• Nitrite 0
• Ammonia 0 (before spike), 3-4 (after spike)
• KH/Buffer 40
• Water Temperature 79F
• After the white fuzz mostly disappeared from his head this morning, I noticed a deep pink gash where the fuzz used to be above his left eye. This was the second time I tried treating this fish with Maracyn Oxy. It appeared to have treated the infection the first time I quarantined him, this second time is when I saw the gash, though I'm pretty sure the ammonia spike is what did him in.