Looking back through the photos you've posted over the weeks, they look like they've been pretty stressed since flowering began. Without knowing the details of your grow, it's hard to say exactly what is going on. It's likely too late to address anything this grow, but there are a few things you may want to consider for next time.
1) The first thing that stuck out is 12" is very close for a 100W LED light. Even the cheap purple LEDs of Amazon should be at least 16" away and I usually shoot for 20" or more. If the lights are too close, the plant can get stressed and any issues at the root level (out of range pH, overwatering/underwatering, etc) will be much worse.
2) Are you checking the pH of your water? For soil it should be between 6.0-7.0 with 6.5 being a safe number. Most nutrients can be easily absorbed at 6.5. Anything significantly lower than 6.0 or higher than 7.0 can lead to nutrient lockout.
3) How much and how often are you watering? By the time they're flowering, you want to give them a good soaking (I usually do 1-1.25 gal every 2-3 days in a 3 gal fabric pot). Lift the pots to see how light they are and water when they're feeling light. You don't want them to dry out complete, but you do want the roots to get oxygen.