Fast yellowing in older and middle leaves, small buds.

Hey Spiral, this is a tough one and the rapid development indicates rapid action should be take to save your efforts. Given your light-data I too don't think its light stress. The leaves look a little droopy which is typically not a sign of light stress. Droopy leaves can be a sign of overwatering, underwatering, or a root zone issue. Also, since it's an organic grow nutrient availability could shift quickly if the organic matter isn't broken down into usable nutrients quickly enough. This would also fit in with the Buds not fattening. But, if I had to bet my money on one of the above, I'd go for soil PH since all of your plants show these symptoms simultaneously. Soil pH directly influences the availability of nutrients across the board. Even with regular calibration of pH measuring tools, the actual soil pH can shift, particularly in organic grows where the breakdown of organic matter can alter the pH over time. Microbial activity can vary across different spots in the soil, but pH is a more systemic factor that can uniformly affect all plants, especially if they're all in the same soil mix and under the same watering regimen. So, focusing on a thorough check and adjustment of the soil pH, could be the way to go. Best of luck! Cheers, D.