Glueberry OG - Organic Outdoor

Things are mostly going well with these 3. It's been extremely hot and humid, and they've been thirsty! Number 1 has been yellowing drastically, very evenly from the bottom upwards. It's like she's drawing on the reserves in the fan leaves, for some reason not getting enough from the soil perhaps. I upped the fish emulsion, and gave an entire extra feed of everything this week, so there is definitely no lack of nitrogen and phosphorous. It could be calmag deficiency, but I have been giving a healthy dose of blackstrap molasses for a while. I tried a teeeeny bit of epsom salts on just this plant, 1 tablespoon per gallon. I don't want to use too much of it since it could hurt the microbial life, but at this point I'm open to options. She could also be rootbound, possibly 70L is not enough grow medium? Although the other 2 are fine. I have only a few weeks left, hopefully there's enough goodness left in the fan leaves for her to take whatever she can't get from the roots. I do also have an ant colony living in the bag. Hopefully they aren't causing problems. Cheers for now!