attempted re-veg turning brown

so plant has been under 20/4 for 2 months..no good new growth..slowly turning light brown. like all the chlorophyll was being sucked out. went easy on ferts..i tht..temp 80+ rh 60-70%. in promix hp or bx in 5 gal pail..plenty of holes in bottom.....have 2 others meeting same fate...turning brown like a raw rolling paper kinda brown..what the heck am i doing to kill em? i hardly ever ferted em but saw hints of new growth,as it turned brown, so gave em a lil juice. then saw new growth going downhill so tried to rinse the juice i gave em out,GH flora trio series juice BTW under a 240 HLG turned all the way down. thought root rot so i drilled holed up side of bucket hoping to dry it out faster...any other ideas? I kinda want to keep this one around. thx..

I always up pot to reveg and trimming roots and adding fresh soil works as well

well it aint dead yet so ill try that. my pots are usually large..like i use a 2gal then plant into a 5 or 7 or 10 gallon but when i yank out rootballs they always take the 2gal shapeso maybe i gently yank a live one and put in fresh soil..cant hurt it much more rt? it'll either find a way or find a compost heap. lol.. thx for the reply

If you throw it in the compost heap...check back in 2 weeks, my yard waste corner has brought more than one back around.

nice surprise?