single measurement is not ppfd. That's umol/s PAR or PPF or PPE. Sounds picky, but significantly different. Enough for this context at the least. Use resulting node spacing to guide light intensity adjustments... take notes. easy to rule out in future as a cause of anything. Then take some measurements at various stages - less is needed earlier but quickly ramps up.
Suggested DLI is just that... The max you can give daily before it causes problems or photoinhibition is a product of temp, rh and co2.
did you drip something on it? use some whacky foliar spray? Fan directly pointed at it?
a lot of people struggle with the basic concepts of irrigation too, which could contribute to this sort of issue
1) fully saturate - never partial, never spritz. if soiless, also get 10% runoff
2) Wait for appropriate dryback/loss of weight and repeat.
Don't overthink irrigation. it's simple, not sophisticted and complex.