wut is up with my plants 3erd round same thing

ok i can veg perfectly fine, green healthy robust growth all through out vegging but at about 3 weeks of flowering my buds do exactly what you see in the pic and it gets worse, its really anoying and i KNOW its affecting my yeild how do i fix this?

heres my setup 4x4 room 1000W HPS in a air cooled hood about 30in away from tops cooled by its own fan and a 2end fan to exhaust the tent, im running co2 @ 1100 PPM with a controler and all that fancy bullshit my regular temp is 75-85 day, humidity 30-50, ueseing foxfarm ocean forest with sensi bloom part A&B and bud candy, 3gal buckets, and strain is master bubba kush

i feed every other watering with a PH of 6.8 give or take, what am i doing wrong here?

do you ever flush b4 you flower? here is my THEORY....the plants eats the nutriens in the soil or medium, and its waist i believe is water and oxygen...the water come out the roots...and i assume is comes out extreemly acidicy, so if you dont fliush the acidic waist water from the roots it can ultimately cause lock outs and all kinds of deficiencies....

maybe you can carry your veg formula into the first couple weeks of flowering, that may help. how old are the plants in the pics, they look more than 3 weeks in? Do you spray with anything? Is you water filtered?

they look hungry. whats your ppm?

i do flush i normaly give them a good ammount of just PHed water every other feeding the pics of the plants are around week 6-7 they are at like week 12 right now and look ALOT worse, im not sure what my ppm is im ueseing brita filtered water and i allso foiler feed with just ph water every few days during the morning time

You ever take the root zone apart after a grow and check for root rot or bugs?

Get a ppm meter