2000 PPFD is way too high for an average 12-hour flowering period. What Bugbee says in that video, if you watch the whole presentation, is that cannabis plants can handle up to 2000 PPFD – which is about what the sun produces at midday in summer at most latitudes – but that it is only for a short time. What's more important is DLI, which is the total amount of light over the 12-hour period. If memory serves me correct, 40-45 DLI is what you should aim for, which is an average of 1000 PPFD over any 12-hour period, up to 60 DLI (1400-1500 PPFD) if you are using CO2.
We've commented before on some of Bugbee's videos and while they are great for beginners, we believe some of the information he presents is incomplete. For example, green light is much more important for plants than simply aiding human vision, as Bugbee states. It is not only the most efficient spectrum in terms of photosynthesis – as it penetrates the leaf surface to activate chloroplasts below the surface – it is important for diffusing light throughout the canopy (which is why leaves are green, because they reflect light to other parts of the plant that are not in direct sunlight). I've also read that green light regulates some hormonal responses in plants that support the immune system and improve health.
Regarding the THC content not being affected by blue light, there are two points. First, the plants shown at 14:50 onwards are CBD rich – there was hardly any THC in them to begin with – so they are already at a genetic disadvantage. If you are trying to grow THC, after all, wouldn't you use a high THC strain to compare? Secondly, Bugbee doesn't state which "Blue" was the control; ie, was it straight 450nm or was it 400-500nm? All the experiment proves is that possibly 450nm (if that was the type of LED being used, which is highly likely) does not have as much effect (although isn't it interesting that, despite what Bugbee says about margin of error, there is still a variation in CBD levels of 6%?). Meanwhile, other tests on high THC strains have shown that there is an effect – especially in the blue area <450nm. See the other links in this thread for those tests.
For your 4x2 you should probably talk to
@Prawn Connery, as he also grows in a 4x2 and is running about 340-350W at the boards. I suspect you are simply running too much light in there with the COBs that is stressing your plants.