Best bet is to find a nutrient that self-buffers, and one that is designed for hard water. Even if you pass the water through reverse osmosis, it doesn't change the alkalinity, but it does make it easier to buffer one direction or another. With well water, you want to use the nutrient at the lowest dose and use it every time you water. It will act both as fertilization and as a water conditioner. Raise the nutrient dosage as the plant gets larger/looks like it needs it.
Another thing you can try when your medium is alkaline is to top dress with a little gypsum, then do what I said above. It won't change the PH of your medium, but it should free up nutrients that are locked out from PH issues, and allow them to be locally uptaken by the roots.
Finally... hate to ask, but how long has this plant been vegetating? It has a look like it has an overgrown top canopy which is not letting enough light penetration, and so you get lower canopy die-off. You'll want to trim that out, probably thin the upper canopy as well, and let the plant re-focus on fewer growing nodes. Don't be shy!
Also check the root ball... Is it root-bound? Once the medium is filled up and choking on it's roots, things like that also start to happen. I've been there a few times due to neglect for sure.