My fan and sugar leaves are turning brown/yellow about 5-7 weeks into flowering HELP!

I am growing Aurora Indica X El Dorado under 400w HPS in 3 gallon pots. I had veg'd them for a good 3 months (per wifes orders, couldn't put up the HPS until I bought a tent & Air scrubber), so they were under 80w CFL and two 80w Leds for a while. Put them under the HPS End of may/beginning of June. Nutes: FoxFarm microbrew/Grow Big/Big Bloom. Temps are right around 70-80 with regular air circulation. I have a feeling that the pots are too small and must repot in 5 gallon so the roots may grow more. Could be nute burn, still new to this. Regular feeding schedule every other watering nutes are used. PH 6.5 roughly

Pics are of the worst looking plant the rest don't have and burn on the sugar leaves just some yellowing on some fan leaves.

plz help! Thanks in advanced!

root bound and definitely nute burn

looks like too much nitrogen as some of the leaves are over dark green

First pic looks like it has been too close to the light. But you are close to harvest and can expect fan leaves
to yellow and drop off at this point. However, I believe in removing big leaves after they are more than 50%
dead. You could stand to pull off them off. Remaining problem is curling leaves on purple plant - by any chance did you spray
them with a "mild" nute solution? I did that once and got leaves like that. Burnt from too hot nutes.

It's too late to transplant, eh? I would flush them good at this point and give them just water from here on out.

Good luck, BigSteve.