Columnaris can be seen as bleached spots, fuzzy cottony spots, or spots on the body of the fish... Is there a chance that could be it? Has any fish died recently, or anything that fouled the water? is the tank cycled?
What is the temperature at? Keeping the temperature at 76 is fine, and will work to yuor advantage to have the temperature a little lower than usual in columnaris cases... some people recommend copper-safe stuff but I've heard it is hard to regulate and dangerous! I fought the strangest looking columnaris, with cold water (had my female bettas in bowls), daily water changes, and AQ salt. If someone else has a better treatment they should say so :) I rarely deal with columnaris.
I also have heard of Maracyn and Maracyn 2 used in combo for columnaris.