At the beginning of your quest it looks like you just got caught with a old bag of soil, that most likely got saturated more than once so more nutrients due to over cooking were available to your young plants. Been there, and had to deal with that many times over. But once they build enough of a root system they will work their selves out of that and they seem like they have done just that. Other than that, FF soil and soilless mixes by default never have enough calcium or magnesium. so you should always add a supplement of those two secondary nutrients from day 28 until the end of week 7 so you avoid the common mag and ca deficiency that can incur when you grow certain strain, really any strain that has Afghani in its linage. And I always use 3ml ca/mg + and I also add 1/2 tsp of Epsom salt to every gallon of water or feed as preventive medicine, to stop those common mag and ca deficiency that can happen more often in FF soils, and is now happening to your plants. So add the supplement I suggested and it will fix your problem. And as for watering your plants, always saturate them until you get like 10% runoff. And as a general rule a 5 gallon pot will need 1 1/2 gallons of water to be fully saturated. And do not water them again until they have pretty much dried out. Lift each pot to check that, they should be super light before you water them again.