I can think of three strong possibilities...
Possible overwatering.
Possibly rootbound.
Possibly just needs to recover from the flush. I've used Fox Farms products for the past few years, and give a good flush monthly to alleviate the salt build-up that Fox Farms is notorious for. Sometimes the additional (prolonged) moisture in the soil stresses the ladies a bit.

Will be a couple of weeks for all the nitrogen in the soil gets used-up from your last application. Once used-up, fan leaves will start to yellow, as the plant scavenges those leaves for it's nitrogen.

oops...I just noticed...you said soil ph is 6.5...? Are you using one of those soil ph probes that are notoriously inaccurate? Can you ph ingoing and run-off ph?

Any other additives, like molasses, micronutes, Sweet...?
Rusty Trichome Reviewed by Rusty Trichome on . new growth rolling in, but no yellowing!!!! They are: 1 week into flower under 400 w hps/18 inches away from canopy trainwreck x big bud 2 feet tall 3 gallon buckets Why is the new/young growth rolling in on the edges and droopey? the big fan leaves and older foliage does not look fucked up. this is occuring every where on the plant, top to bottom.. the soil ph is at 6.5. temperture 71-75 (possibly low 60's at night)degrees farenheight, im using fox farm tiger bloom, but used fox farm big grow right before flowering , which is Rating: 5