I agree with you 100% you need to jump into a bigger pot ASAP. Have you lifted a plant out of the pot to see if the plant is root bound? I think it is
Now your in coco still correct? If so you can get away with a smaller pot because of the media but I would jump to 5 gallons still. Or go 3 to 5 gallons.
Also I’m really not joking it’s been a long time since a product really impressed me and it’s fish shit. If by chance this is a ph problem it will aid in that correction naturally.
I don’t think it’s a light problem.