Bud density not there yet any suggestions SCROG Grow

Hello all, I am in the middle of my first SCROG actually at the tail end of the grow. I am growing master kush 4 plants in a 3'x6' screen 2 600 hps lights 75 F 50% RH constant I used GH Flora series 1200ppm 5.7 - 6.0 ph. They were flipped on 8/9. Here is my concern, all of the buds are very streatched or airy there is no density to them. They look like there is a light leak but there are none. I have just cut back the nutts to what they refer to as rippen but it is basically all grow and a little micro and the ppm is 850. from what I can gather they have about 2 to 3 weeks left. Any ideas on what is happening? Prior to yesterday (solution change) I was running about 1250 ppm with a higher amount of N and P. Do you reduce your ppm at the end of the flowering stage? What causes the bulking up of the bud vs the growing of the bud. Thanks in advance.
Kevo

i know you can add density with CO2 icant remmeber the amount i think its like 1200 ppm is perfect or something very close to that. over doing it can fuck shit up worse though./

you shouldnt be adding N at the end of flowering.
You should be cutting it out entirely.

Flower boosters usually contain potassium and nitrogen.

light leaks and high heat can also cause problems for bud density.

A big issue could also be genetics.
Some strains just want to be fluffy!