@cynthiaofstedal hello and welcome to connect. These are all pretty common complaints with anti-estrogen therapy, and even more shocking if you had not already entered menopause.
I found both of these things to be true although since nails are dead tissue and only grow so fast I did not have nail changes that fast from anti estrogen therapy. However, I had very fast changes with the nail bed from pretty much every cancer treatment I have had including anti estrogen treatments. My solution has unfortunately became over time to keep my nails very short so that I don’t break them lengthwise creating pain.
Have you had any other systemic cancer treatments? Could this be a change to the nail bed, creating a weak nail?