Yo Red Admiral, just to give you my input, I think DPhipps has hit the nail on the head with his last suggestions - firstly, don't water every day (like he says, every 2 to 4 days is fine), as soil grown cannabis does prefer distinct wet & dry periods. Secondly, don't add nutrients with every watering, as it then saves the soil becoming too overloaded too quickly & gives you abit more of a buffer - certainly, some growers do add nutes every watering, but you've really got be 100% accurate with actual required levels, and if you're not then it usually causes more problems than it solves.
The way i see it is, it's always better to underfeed/underwater than overfeed/overwater, as a plant will still grow fine underfed, it'll just not be as much weight, whereas an overfed plant will have trouble growing and may not end up producing any weight if it's medium becomes too cooked by nutes. Plus you'll learn alot easier about feeding if you essentially don't feed, wait till you see a deficiency response in a plant and then add a little bit, compared to feeding recommended dosage amounts straight away and trying to work through the confusion of signals of what the plant is actually saying to you. It's alot easier to learn over time if & when something needs to be added, rather than if something needs to be taken back out again.
In general, your leaves look fine, so i wouldn't be too worried about nutes right now, and you could even do half the recommended bottle dosage for awhile, as they don't look like they're crying out for nutes, and that again gives you bit more of a buffer safety zone.
The other thing i was gonna say was 1.5L waterings, even every day, probably isn't going to be saturating those size pots all the way through, which does also risk less root development, as if the bottoms are never wet then there's no reason for roots to expand down there. Underwatering can often look like over-watering in how your plant signals it, though since you say pots are very light usually, then i think yours are probably just not being watered properly, rather than necessarily being overwatered.
For your babies now though, i think your idea of increasing watering amounts to 3L is a great idea, as that should be enough to mean you start seeing abit of run-off from bottom of pots which is good, and if you combine that 3L amount with Dphipps input of watering every few days and interchanging between 1 plain watering and 1 nute watering, then i think you should see them start to perk up fine!