torn fins? tail bitting? or curled fins?

[Fasht]

I'm soo happy that my Bleu has finally started making his bubble nest but I guess there's a consequence.

can anyone identify what ever it is happening on his tail? and the ways to avoid it? and how to properly nurse his tail? thanks

Housing
What size is your tank? 10g
What temperature is your tank? 78 - 80
Does your tank have a filter? yes
Does your tank have an air stone or other type of aeration? no
Is your tank heated? yes
What tank mates does your betta fish live with?ghost shrimps and apple snail
Food
What type of food do you feed your betta fish? pellets and dried blood worms and frozen blood worms
How often do you feed your betta fish? twice or thrice a day

Maintenance
How often do you perform a water change?twice a week
What percentage of the water do you change when you perform a water change? 50%
What type of additives do you add to the water when you perform a water change? water conditioner and nutrafin plant grow
Water Parameters:
Have you tested your water? If so, what are the following parameters?No

Ammonia:
Nitrite:
Nitrate:
pH:
Hardness:
Alkalinity:

Symptoms and Treatment
How has your betta fish's appearance changed? his tail started to curl a little
How has your betta fish's behavior changed? he's happier I guess since he made his bubble nest
When did you start noticing the symptoms? about a week from now
slowly and I only noticed it really badly recently.
Have you started treating your fish? If so, how? I did contaminated him for 2 days with aquarium salt prior to this situation
Does your fish have any history of being ill?no
How old is your fish (approximately)? about 3-4 months?

[vilmarisv]

Is it really curling? It's hard to see from the pic... it looks more like shredding from the pic.
Salt will not curl your guy's fins but changes in the chemistry of the water you're using might.
Curling sometimes will never go away, best thing you can do is keep his water as clean as possible.

[Fasht]

it might be a lil bit of shredding and curling, maybe because of the DIY Co2 that I newly setup on the aquarium I heard this lowers the Ph of the water. Our tap water is 8.0 ph then when I tested his tank it says 7.8. what's the ideal Ph for them?