Toxicity, Deficency? Overfed, Underfed? Lighting issue?

Looks like too intense light with no enough nutrients to compensate for it

Lemon strains do not have yellow leaves…that’s just complete BS. Look at the lemon orange in my profile. It’s deep purple, green, and red. My paradise pine is like yours. She had an abrupt, unintentional start to flower for a couple of possible reasons but I think also led to its yellow leaves. I think my issue is possibly a root problem.

I only see nutrients listed under the most recent week, not sure what you were feeding before and at what dose so can't tell if you cut to much of some nutrients or added to much of some. I see in your diary you're running your light at 10" height and 100% power, that's way to close for that intensity IMO. Your leaves will start yellowing and browning under to much light. I see they're also starting to "taco" because of it. I would drop the intensity to 60%-70% and see if the leaves improve. If anything, the light stress might go away and uncover another symptom that was hidden by the light stress.

Sign of rapid grow if your plant is getting lighter in the flower push. Purple stems can be just genetic, especially if they purple liks yours, nothing to do with nutrients. I would not change a thing a smoke a big bowl

Lemon strains do not have a yellow tinge, the are called lemon due to their terpene profile, not their colour.

Starving for potassium and phosphorous..........and nitrogen to a certain extent, probably due to switching to bloom nutrients too early. Cannabis still needs adequate nitrogen in early flower and bloom nutrients shouldn't be started until there are small "budlets" developing first and not as early as when the first pre flowers appear or as soon as you switch to 12/12. Next grow, add a P/K booster to your nutrient line up for the flowering phase, unfortunately it is now too late to "rescue" these plants.

She possibly needed a bit more nitrogen than she was getting when she entered flower.

Most definitely a deffenicy make sure your giving a bloom type nutrient and cal mag use instructions on bottles if your already doing this then I would increase amounts your feeding. Also check your run off water ph you could just have a soil ph problem starting to cause lockout Usually when you have a ph problem you will start to see spots that look like burns starting from bottom the plant going up slowly then faster Most likely it's just you need more nutrients your ladies are putting on weight and they need extra nutes to deal with making all that plant matter

Lemon strains will have a yellow tinge i hesitate to say feed her she looks so regal and grand id be hesitant. Maybe try a conditioner like fish sh!t