DWC ROOT PROBLEMS - Advice please = )

ok here is where i am at now.. I have numerous clones (rooted about two weekds ago)
all clones were taken from 2 separate mother plants (Golden Goat, and Purrple Urkel) .. I transfered them into Some small Dwc buckets (2 gal)

Basically about twenty percent of my clones havnt really grown since I put them into the buckets a week ago.. where as the other 80 percent look awesome and have been growing about an half inch to inch or more daily

all the buckets had the same nutes, same ph etc.. so im a little confused as to why about one out of every 5 is having root development problems

upon looking at the roots. they look kinda yellowish and when i touched them they were brittle and crumbled..

the other plants (80percent) the roots are bright white with great root development
..

Ppm is low.. ph is 5.5
all the nutes are the same in all the buckets.. i check the ph ppm every other day..

I have no idea why its happening, any help or advice would be greatly appreciated..

any light reaching your water?

hydrogen peroxide [h202] will help your roots. You'll have to search to see the correct dosage i can't remember.

1 in 5 really isn't that bad. just take some extra next time and keep the healthy 1's. but 1 in 5 really isn't that bad man.