Don't know much about well water.
I would do a thread in tropical discussion about well water.
You need to test the well water in ph, nitrite, ammonia, also maybe heavy metals.
Also well water can carry parasites.
Do you run the hose before adding it to the tank, to clear the pipes throw.
Do any fish show these signs.
Darting, erratic swimming, turning upside down, excess mucas, greyish film on fish, or milky substance on fish.
I wouldn't advise 70% water changes, it's to much. It can alter tank temp to much.
You can only get away without water conditioner when preforming very small water changes.
Also need fresh water stats.
The only problem is that bad water quality can show the symtoms you are describing.
Laboured breathing, swim bladder, heavy breathing.