I know you said you STARTED flowering @ 1/4 nutes, but where are you now? Please disregard what bonjo78 said above. This IS NOT a potassium or phosphorus defeciency. If you listen to this, he will only help you burn your plants further. You are currently experiencing a very bad nutrient burn. It is my feeling that you have been feeding at stronger levels than what your plants can absorb and they are starting to buildup nutrient toxicities which is now causing lockout & burn.
You want to FLUSH
It helps if you have a TDS meter to test PPM
If you do, begin by testing the PPM of your regular water used (0-100ppm)
Now start flushing your plants with this water, until water begins to runoff from the bottom of the pots
Gather this runoff & test it with your TDS meter. This is the PPM of your soil. If it's over 750 in veg, too high, 900-1000 in flower, too high
Continue this water flush for about 5-15 min. The color of the runoff will help guide you as to how long you should run water through. Pending how well your pots drain, you may have to turn the water on/off for a while and therefore take longer. The runoff should start as dark, brown, amber colored, moving to a more clear, lightly tinted runoff once it is well flushed and close to neutral.
If you have a TDS meter, again, gather runoff at the end of flush and see where you are at. If you are close to the PPM of the water used for the flush in the beginning, then you have successfully completed the flush.
From there, make sure you don't water much over the next few days or until water/soil moisture is back to par. You don't want to overwater your plants and risk drowning.
ALSO, your soil ph being @ 6.2 is too low. You want to aim for 6.8-7.0 range. This is ideal. Try raising your ph. Even adding some lime, hydrated lime, dolamite will help as a soil buffer to neutralize soil & bring you back to the 7.0 level. This should help, as well.
Hope this all helps homes and that your plants recover! Glad I could catch this before someone who's just trying to quickly comment and rack up posts on here for a higher status led you in the wrong direction that'd end up in you hurting your plants more. Some people just don't know any better.