pool chemicals! oh no! FLUSH NOW!!! that is NOT good for plants. Gotta use plant up/down.
Boiling doesn't remove nutes. Flsuhing does. Heat does not break down chem ferts or remove them.
Don't worry about softening water unless it's realy bad. If it is, you might consider a RO system for your house or going to bottled distilled water. With either, you must add calmag plus. BUT....
Generally, hard water is fine in soil situations. That isn't your problem. It would be if you were hydro.