I like the kiddie pool idea!
Hey @Yozhik -- things looking any better these days?
I think Wile and Pop22's ideas are pretty good.
Outside and root trimming just sound like .... a disaster waiting to happen.
You don't want to be carrying those monster girls inside and outside everyday.
(I'm doing that for 3 tiny micro photo girls right now, and that's already a pain....)
The watering from the bottom, kind of flood plain them, idea sounds great.
The autopot system sounds good, but prob other systems too.
But... now I know that they're your plants and you know them well,
and I'm just sitting out here in internet land, but...
is it really due to being root bound that they're having these problems?
My experience with root binding is just that they kind of slow down growth more and more.
And if the nutes are all used up, then the usual deficiencies.
But the defs can be resolved by feeding.
So I am wondering if it's not a pH thing?
But no doubt you've already checked all that -- pH and pH out... so...
Like pop22 said:
"When the medium starts to dry, EC goes up, and ph can spike up or down..."
So that will change pH during the day.
Not sure what time of day you checked the runoff pH, but may change.
Sorry if I'm out of line here. Just hope that you can get these girls healthy again.
... get a kiddy paddling pool drop all the pots in it and use it like a flood table??