In my previous grows, I've tended to keep light levels on the lower side of the recommended range. I can't say why, frankly, but for my current Gorilla Glue grow, I decided to change that and went with a DLI of 25 on an 18/6 schedule = 385 µmoles.
If you're at 220 and 18/6 which is 14 moles. That's about the level I was using last year and I gradually increased that light level until I got well into veg. That won't hurt cannabis plants but, assuming that you've got the other environmental factors under control, I've never seen any recommendation that would go against you raising your light level. Try bumping to 300 or 400 and see how the plants react.
I ran into an issue last week where my Mars SP 3000 went to full power and I wasn't aware of it until I saw that my tent temperature was heading to 90°. When I got into the tent, one of the leaves had rotated around its petiole so as to avoid the light. Twenty minutes after I reset the light level, it had rotated back to about 30° above horizontal and, twenty minutes after that, it was back to normal. No harm, no foul.
There recommended range for seedlings varies from 100 to 300 to 100 to 400 from sources like LI-COR and Photone. Most of LED manufacturers that I've looked at don't use µmols or moles. They give recommended hang height and dimmer %, instead, but when you get their PPFD maps and run the numbers, they tend to be on the lower side. One reason for that could well be that they want to ensure a successful crop but have no interest in recommending anything more than that - there's simply no upside for them.
I followed the manufacturer's advice pretty closely but, with this grow, have completely changed my perspective. I've stepped away from what Mars and ViparSpectra recommended and have gone in the direction that the "instrument industry", for want of a better descriptor, and what other growers have recommended which is 25 moles. A big factor in that is my third grow in 12 months so I've learned a lot and am more comfortable with what to do/what not to do.
My GG's germinated on 3/15, a few days before yours, and they're getting a PPFD of 450 from the Mars SP3000 plus roughly 100 µmols from a blue LED that I run a few hours a day. All told, they'll get ≈ 30 moles. That's "a lot of light" to me but I can't find any source that says that's too much light. I've attached some bits and pieces that I've collected. These are some of the "inputs" (I've been a programmer for 30 years so I tend to think in those terms) that have helped shape my opinions.
The DLI Levels by Growth Stage is from the folks who sell Photone. I've drawn a few lines on the graph to indicate where my light level should be. Thirty moles this week and then 40 the week after. You might want to check out the Photone site - their site is well laid out, informative, and easy to read.
The LICOR poster - LICOR makes light measuring instruments, along the lines of Apogee.
The final pix is of my GG's today. A comment that I made on another site is that if those plants got any happier, they'd have to get a room. They were at 28 moles yesterday, bumped to 30± today.
