I've no experience with root-pruning but know that bonsai artists use the technique. I think you should google it because I'm not sure what precautions to take.
If you want to go a simpler route, I'd buy a bottle of Cannazyme and use that. It frees up the nutrients bound up in old, dead root matter within the soil and buys a lot of time. It also effectively gives a bit of space. I use it on my Christmas cactus and they like it too.
Just a bit of caution, after applying Cannazyme, CUT BACK on your nutrients because there will be extra in the soil!!!
I still think that your moms need to be regenerated. My friend has a commercial-sized grow and also needs high numbers of clones on a tight schedule, but he keeps a bunch of mothers that are no more than 3' high and replaces them when they look scraggly. Having extra moms allows for a failed run of clones, and more time for the mothers to recover or get big enoug to use.
stinkyattic Reviewed by stinkyattic on . What to do with these moms? Looking to get a few sick moms (SAGE x Sour, AK48 and others) ready to clone and then toss. At five feet they were: - Rootbound in 1 gal containers - Never flushed in their lives - Had a bad mite infestation. - Showing severe zinc def, among others The mites are under control with a combo of pythrethrin bombs, NPS, neem, daily water baths and 85-90% RH. I've heard a few things on what temp....cool or hot? It's set to 70F right now. They were flushed yesterday with 7.0 water at 1ppm, Rating: 5