Beginner's Luck?

I'm seeing three possibilities and I think they're all mildly going on at once, slightly over watered, too warm/much light, and possibly too much cal. It doesn't look like a loss however. The way the leaves are curling make me think you might have an excess of calcium. I'd pull the cal-mag out for a feeding or two, there should be plenty of calcium and magnesium in your soil for the roots to grab no reason to force it. I've always used Cal-Mag as a backup if the leaves weren't pulling enough N from the soil as opposed to a regular feed, maybe 3 doses in veg and never in flower. Just food for thought. I've got some girls that I'm running for the second time, they are about to enter Week4 since leaving the cloning chamber. They're barely drinking, it's just their strain. I know from their older aunts that I'll see roots coming out of my cloth pots in Week 5-6 out of the chamber and at that point they'll be drinking at least a quart every other day. If you're in doubt I like to water my plants to where the soil feels like it's got the same moisture as if it were still in the bag, slightly moist but not wet. The next day it'll be edging towards dry the first 1" down in the soil. That's when I water. If it's still wet on day 3, I pull back the amount of water they get. My last feeding was 16oz per plant, that was three days ago, they'll be thirsty in the morning; and I'll be pulling my solution back go 8oz so they want water sooner and don't go for 4 days again. Maybe also pull the light back a bit, 300w at 9" is a lot of light for such young fragile cuttings. By the Vivosun 300 chart at 9" you're getting around 1500ppfd at your tops, ideally you want between 300-500 ppfd in early veg which for your light is 24". At the end of week 3, I've got my 135w HLG B-spec at almost 17" and even then I'm running it about 40% power so it's turned down to get a ppfd reading of about 500-600, which honestly is still a bit hot but I'm pushing hard for nodal development. You don't want 1500 ppfd on your plants until they're in flower and every aspect is dialed in probably including CO2. Most charts say 800-1000ppfd for flower without Co2. Look into Korona cell phone App. The different modules are like $10 and you can get a "rough" reading from your light with it. It's what I use until I can find the scratch for a $500 ppfd meter. Maybe for the next few waterings give it a plain water pH to 6 - 6.3; not a soak just a gentle watering a few inches out from the main stem, let your roots find the water don't saturate them and keep them in one place, they like to hunt for water. Most soils out there have enough nutrients in them to get a strong clone to at least Week 2 if not 3. In a 5gal. Your roots haven't even found the end of their Universe yet. Random and won't have anything to do with their health at this stage but I like to plant my clones right up to the bottom of their first node, the stem will grow roots out above it's initial root-ball. My current mature flowers have roots webbing the top of the soil and dangling out the bottom of the fabric pots. Each time they were transplanted I basically buried the main stem as deep as I could without covering leaves in soil. Best of luck and don't worry, they don't look too bad. Maybe a bit too loved, but we all start out with too much love for them. Less is more most of the time with these girls.