It sounds like it's time to fertilize. In one quart containers, I'd consider giving them a quarter teaspoon of a fert like Peters 20-20-20 mixed. in a gallon of water. If you have a tds meter, add fert to a gallon of water until the number is about 750. Perhaps fertilized every other time you water, or every third time. That kind of thing. I'd consider putting each plant in its own 5 gallon bucket with a cup of Whitney Farms powder fert mixed in, or something like it, like Foxfarm powder which I think is 4-8-7.