I hope the picture I've attached is good enough. To the naked eye, it looks like he has little bits of dirt around his face and on his scales. I've been looking up pictures of all types of infections and diseases but I personally can't tell what this might be.
I've had this betta for two weeks and he has looked like this since I got him. I tested the water he came in and they weren't great, so I thought some time in better water quality might be all it needed to clear it up, but it has neither improved nor accelerated.
He is rubbing on decor and darting away. This is what is worrying me most, even though he doesn't do it constantly or even every day as far as I know. Just occasionally I see him get agitated and start rubbing and darting. I most recently saw him do this today, and the earliest I saw him do it was the second day I had him about 2 weeks ago. Also, not sure if it's related, but last night he ate a pellet and suddenly darted around, looking really uncomfortable, but then settled and came back for more. Otherwise, I haven't seen any behaviour issues. He's curious, active, unafraid, and begs for food.
Current tank parameters are pH 7.0, ammonia, nitrite and nitrate 0 ppm
The tank is 7 gallons, it's been running for 1.5 months. Stock is 1 betta and 5 cherry shrimp.
I've been doing a 30% water change every 3-4 days since I got him to stay on top of the water quality.
I've only been feeding him Hikari bio-gold betta pellets so far.
Thanks for reading and please let me know if there's more information you need.