Post water perameters. Ammonia, nirtite, nitrate and ph.
This is columnarus. Do a 50% water change, lower the water temp to 72-75 and add salt at 1 tablespoon per 5 gallons of water. Your water perameters will dictate the best med for this. Furan 2 is good at lower PH levels of ~7.2 and lower at Higher ph Triple Sulfa is a better choice. The combiation of Kanamycin & Furan 2 is great combination, Kanamycin can also be combined with 3X sulfa for use in high ph where Furan 2 is ineffective. If you lower the temp add the salt and change the water you sould be ok with either the Furan 2 or 3X sulfa depending on the Ph if you can not get Kanamycin.
If you can't get meds till morning it is imperative you lower the temp and add the salt to slow it down. It will kill quickly if you don't.