Help please, sick betta

[tatianar]

Please help. It has gotten worse but at first it was a tiny spot. She’s obviously sick, i moved her to this cup because she’s in a 49 gallon and i don’t want my others to get sick.

 

[WildFish99]

Looks like a fungal infection. Treat with fungal all or with whatever fungal treatment you can find in accordance with the box.
Until you can treat with specific medications stick to stuff that should broadly target it and increase the slime coat.
Here google may be helpful.