Turned out I was frustrated enough with the poison-pickers that I took another whack at them. Not just colours, but linework too. Number three, the only one I was really happy with had the privilege of remaining unchanged.
Number two got an extra line or two to make her sash's path a bit more obvious, and raggedied to look less like an apron. And a hat of course. A hat that screams "witch!".
Number one's still a bit dodgy in my eyes. The strange poofy hat is... strange and poofy. But I'm much happier with her mantle and torso now. The colours aren't ideal, but I can live with them.
I even put some extra crease detailing on the cloth. Nothing for number one unfortunately, but I'm much happier with these three as a set. They look witchier to my eyes. Even if you start swapping parts about. I've a feeling you could swap legs and torsos separately; they're not built for it, but it wouldn't be a huge mod. Perhaps even the unique details - mantle, gloves and cloak - could be moved about. Possibilities!
Even with #1 not totally satisfying, I'm content say these are as done as I need them to be.