Training a plant is what controls the growth. The only thing a small container will do is lead to it becoming rootbound sooner, and reduces the level of nutrients available, since there's less medium to hold it.
I don't do organic gardening, so I couldn't advise you on what to buy. I buy my nutrients in bottles
Personally, I prefer using 2-part or 3-part nutrient systems, and am currently trying a 3 part nute system, plus a ton of additives from Humboldt County's Own.
I would avoid typical store products, like Miracle Grow. I would also strongly suggest you avoid using any pellets, granules, spikes, or any other types of time release fertilizers. When you flush, it releases a ton of nutes all at once, and ends up hurting,, or killing the plant.
Usual base nutrients in 3 part systems need 3 parts: Micro, Grow, and Bloom. The few I've used and read about require ALL THREE used throughout the grow, but in varying amounts based on the current stage of growth.
IE: less Bloom used in Veg, and less Grow used when Flowering.
For a soil grow, handy tools:
PH meter
Hygrometer (humidity)
Thermometer
and a set of decent nutrients.
A lot of soil growers don't even use their PH meter much, if at all.
My guess is that it's most likely just Nitrogen, especially since they're flowering now. Do a forum search, there's a few guys who have even used urine as a fertilizer, but it has to be properly diluted first, they'll have the info in their topics.
But the fact that they're not taking in water makes me lean towards shock, possibly from being root bound. At the height they're at now, transplanting is not a bad idea, and can only help the situation, if it's not too late.
As for your prior successful grows, you likely had a really good soil that provided the plants everything they needed. But not all soils are created equal, and beyond that, each strain has its own specific needs for nutrients.
Your best bet right now, in my opinion:
#1 Transplant into bigger containers. At least 1 gallon, preferably 2 gallon, short and wide will work.
#2a Visit a local hydro shop and pick up some base nutrients, 2 part or 3 part.
OR Option #2b Find out what organic items you need, and buy those, and add those as soon as possible.
