Rapidly-Worsening Hole in the Head on Acara?

[B1gJ4k3]

Noticed a spot on the head of one of my blue acaras and thought that it might be hole in the head, so I pulled him out into his own quarantine tank and started treating with salt at a ratio of 2 gallons per tablespoon. The spot almost seemed to heal a bit and was almost gone with only a little redness around the area, but then suddenly over the last two days has gotten much worse, spreading to the sides of his head and even some on his body. Unfortunately, I haven't been able to get to the store for meds, but I assumed that the salt would be an effective band aid in the meantime. Any idea what might be going on here? What should I be doing?

Parameters:
pH: 6.8
Nitrates: 25-ish
Hardness: 150
Nitrite: 0
Ammonia: 0
KH/Buffer: Low
Temp: 79

Last week:

Yesterday:

Today:

[Colu]

Possible hole in the head with secondary bacterial infections most effective treatment is metronidazole active ingredient in metroplex or fritz metrocleanse feeding a small amount twice a day for 3 weeks and dose the tank with kanaplex salt is not an  effective treatment for hole in the head I would get the medication I recommended and start treatment straight away @B1gJ4k3

Edited March 29 by Colu