Columnaris will often imatate a fungus, underneath what looks like fungus is a bacterial problem. Try Maracyn & Maracyn II, or a sulfa based antibiotic. Anything that looks like mouth fungus is columnaris.
To drop the hardness you need to start with ro water, and reconstitute or add around 25% tap water. There is nothing you can add to drop hardness, you have to remove minerals to drop the hardness. I wouldn't worry about the hardness.
I would med with the antibiotics, start doing 25% water changes daily for at least 5 days, and don't add any pH adjusting chemicals to the tank.
To drop the hardness you need to start with ro water, and reconstitute or add around 25% tap water. There is nothing you can add to drop hardness, you have to remove minerals to drop the hardness. I wouldn't worry about the hardness.
I would med with the antibiotics, start doing 25% water changes daily for at least 5 days, and don't add any pH adjusting chemicals to the tank.