I would wait until 50% or more of all the Rot Front plants have at least one open flower. Then top them. If you are going to stalk cut, wait until the upper leaf is showing yellow, then cut and hang. Sometimes the lower leaf is ripe quite a bit earlier than the rest of the plant. You can prime those, then stalk cut the rest of it when they are ready.
I don't think your leaf is yellow due to maturity, I think they are nutrient deficient. They need some fertilizer. They are a few weeks away from being ready. I topped my earliest ones June 2 and I'm still waiting to harvest. That's over a month ago. Mine are close, but not there yet. The one plant with the bud bag wasn't topped and it's not even mature yet. The others are pretty ripe. Topping will get you there sooner. I don't top Rustica.
I grew some Rustica one season about ten years ago. (my only attempt with Rustica, I can't get past the smell lol) I didn't top those. The ones that I was able to successfully cure were the plants that I allowed the leaves to fully yellow on the plant. Then harvested. They were easy to cure. The Rustica that I tried to harvest like they were N. Tabacum gave me fits.