The usual culprit with rising pH is something in your decor slowly releasing minerals. With ammonia, it is overstocking, something decaying and/or inadequate water changing routines.
Ich comes from outside, from the store, as does most fin rot. Very little of what we call fin rot is actually that, btw. Ragged fins can come from shipping or stores.
We all disagree on Ich treatments, every time. I've encountered heat adapted/resistant Ich and keep tropicals that would perish at 86f, so I use meds. But with most Ich, heat will work. I wouldn't do it myself, but you've researched and made a choice that should be effective.