Check what type proteins your present products contain. When/if you start using products with protein again, add one type at a time to see if any of the different proteins is a problem for you.
You might try some Suave Naturals conditioners (not the coconut while you are off protein). They have EDTA (a chelating agent) and may help rinse the hard water minerals out of your hair. Using distilled water for your final rinse may also help. A shower filter may also help.
Experimenting with too many products to name here. All this great info keeps my head spinning.