Pretty sure this is 100% normal. From what I've seen after awhile the base of the stem hardens up and almost looks like it has a papery bark type coating. I'm guessing its just to protect from bugs and give some extra support as the buds up top get heavier, and its normal for lower and older leaves to get yellow and die as there is less light for them to consume and are not needed anymore.

I'm fairly amateur myself so until someone else more experienced gives you the green light you might not be out of the woods just yet, but I'm quite sure you and your lady are gonna be just fine.