Are my plants growing too slowly?

Speed of plant growth- I understand that proper DWC systems lead to bigger, stronger, faster growing plants. They will be 3 weeks old tomorrow (day 1 being the first day that they showed through the 1’’x1’’ rockwool cubes). They look healthy although 1 is more fully developed (the first 1 sprouted when I was not home and went without light for the first 24-36 hours, causing it to stretch 3 or 4 inches in the very beginning. Since then, it hasn’t grown much at all.) My prettier plant has a lot of bushy growth and very short internodal spacing, but it is only about 4 or 5 inches tall. She (hopefully) looks good though! This could be a sign that my 90 watt LED light, which is about 6 inches above the 2 plants, is giving them a very adequate amount of light and not allowing them to stretch whatsoever, which is good. It just seems like I have seen pics of much bigger plants at 3 weeks old, even in soil. My question is, with my setup described, should I be worrying that my plants aren’t growing fast enough and something is wrong? Or should I be extremely happy that my LED light is powerful enough since they look healthy. I know it differs, but how big was YOUR plant at 3 weeks old? And how small would my plant have to be to worry that something is seriously wrong? Thanks! Here is my setup:

- 2 northern berry seeds of unknown gender, germinated by using sterile tweezers to drop the seeds into 1''x1'' rockwool cubes PH'd to 5.5 with RO water, later transplanted into separate black 5 gallon buckets w/ 6 inch net pots full of PH'd hydroton
- 1 90 watt LED light set to a 21/3 timer
- 1 oscillating fan hitting the plants
- 1 HEPA air purifier in between the plants and the fan (to sort of direct the purified air to the plants)
- 1 of the buckets has 1 air pump connected to a micro-pore air stone while the other bucket has a more powerful air pump with 2 lines attached to 2 airstones, only 1 of them being micro-pore
- 1 tiny office fan sucking air out of the room from the top of the doorway in a 5'x5' walk in closet
- 2'x2' three-sided "grow area" in the corner with flat ultra-white anti-fungal paint, only 3 sided so the fans can hit the plants
- AN pH perfect (supposedly) micro-grow-bloom, gradually up to full strength directions on the bottle over a few weeks (although I am currently switching to half strength for sure). I read that northern berry is a thirsty strain and I haven't found very much guidance on dosing with these specific nutes)
- GH rapid root enhancer gradually worked up to full strength (cutting back to half strength now)
- nutrilife 29% H2O2 that I just started using a few days ago, have added 3 mL a day for the past 3 days due to some slight (hopefully) root issues
- room temperatures ranging from 81-85 degrees with humidity
ranging from 40-50%
- RO water in the buckets
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Your plants all look very nice to me other than being no bigger if not smaller than what I get with soil. I think you could use more light, personally.

I am by no means an expert, but your plants look healthy to me. They are smallish and I think Ivan P is right that it may be that you need more light. Here are my latest 12 days in (yesterday):



Your plants will probably explode once they start flowering. I don't have any experience with LED lights, but from what I understand they don't generate much heat. Maybe move your light closer to the plants? I am using a 250w HPS and some snap reflectors (and a small T-5) with CFLs to add some blue spectrum. You cannot tell from the pictures above, but those lights stay pretty close to my plants (about 2-3 inches) and my HPS sits about 18 inches above the tops of the plants. Try moving your light closer and see what happens. Keep in mind, that again, I am no expert. I am only on my 2nd grow, but my 1st was pretty successful.