Ok iv got an issue- need help with my 5 ft-er.

plant is 2-3 weeks into flowering, showing nice little clusters of pistils everywhere. Its in a 4 or 5 gallon pot and is about 4.5 ft high. My problem is pale yellowing bottom large fan leaves that keeps rising. The chlorophyl is just being sucked out, no interveinal or anything just turning pale yellow with leaf stem and dropping. I KNOW its not nutrient prob or ph - iv fed borderline overkill on nutes lately including vegging nutes with bloom nutes to stop it yellowing, and it seemed to sort of halt the process just a little bit, but clearly had too much N in it. So i flushed a couple of days ago and gave a hit of bloom nutes 6.2-14.6-16. Yellowing has gotten worse but plant looking healthier on the top.

Now lately you have been able to see roots appear at the top layer of toil like slightly above the soil which indicates its rootbound so i covered with a bit more soil and due to location and size of plant i cant really repot it especially since i dont want to stress it now its flowering. The compost soil mix im using says its got water retention on the pack, and my pot is in shade all day, so it takes like more than a week - maybe two weeks- for the pot to dry out and iv been feeding more regularly than that.
so maybe its root bound plus roots lacking oxygen???

Either way how can i give roots more oxygen? is this advisable?

any ideas?

if you can cut the bottem of the pot off an stick it on another 5gal thats 3/4full....also your plants need more nitrogen...peace az

no it doesnt

yes it does...you cant expect to give the proper nutes for one week an the problem is going to just stop..that plant it so big that a.your lights aren't hitting deep enough into the canpy b. your not feeding enough nitrogen..like i said as far as the root bind just bog it...peace az

the plant is strange its got only really a top canopy of leaves and light does hit some of the yellowing leaves

3 weeks ago flushed then gave full strength bloom and veg nutes
2 weeks ago repeat
1 week ago repeat
few days ago plant was over nitrogen could tell my leaf colour, and slight burned tips, and dark growth
flushed
gave bloom nutes this week only which are 6.2-14.6-16

plant changed colour very quickly from dark dark green to a lighter green.

i gave 2/3rds strength veg nutes today again....

somehow i dont think nutes are the prob esp that its root bound judging by the roots at the top of the pot, and i cant stick another pot underneath due to location in my back yard it cant get any taller..... already tied down and such

what can i do to give plants more oxygen that i think they require?