RE: medications I heard from numerous Rabbonim that you dont have to tell unless:
1- it effects your life on a day to day basis
2- its life altering
3- its going to impact the life of your spouse.
I’m a firm believer in honesty is the best policy in which case I think the person in the situation should tell the potential suitor once thwy become far along enough that they are comfortable with the person and it would mean something to them. Also, I never understood how you could really build a TRUE relationship with someone if it was based on lies (this goes for medications and OTD, or some other skeleton issue)