So that said, I would drop it to 13/11 now. One crack. I don't think doing that will have any effect on her. The slower you do that first drop, the bigger the plant will get.

After you get stabilized at 13/11, for a few weeks, then comes the slow change.

Like OM, I've grown these puppies outside, and they get big. Stupid big. Unless you have a lot of space, for these plants to grow into, I wouldn't want to doddle around going from 18/6 to 13/11.

If it's not asking too much, do a log of this project. I wish you the best and would like to see how it goes.