Sudden Bacterial Infection?

[Dynamite]

This morning when I woke up to feed the fish all was perfectly normal, Came back a few hours later and my betta and possibly one of the female guppies I believe have suddenly developed this infection.
It is a 30g with live plants, the temperature is at 84*F. Ammonia, Nitrites are zero ppm and the nitrates are 25 ppm, the PH is at ~6.8 I have the API liquid test kit. This aquarium is approx. 2 months old, I had a 10 gallon set up which I tore down when I purchased this aquarium and all the sand plants and inhabitants were moved from there to the 30g. There are corys, black and regular kuhlis, a few guppies and some swords (they are being moved to the 80g once this is fixed) and my one male betta. The last WC was 2 days ago and it was approx 50%, We do a WC 3 or more times a week.
I am going to work on better pictures in a little bit.
Thank you for your time!