clone roots black oil?

man i dont know but,i have 12 clones in one bubbler res,3rd week roots are about 6 inch long i cleaned the res and added ff grow big,bush doc micro brew,24hrs later the roots are covered in a dark brown to black slim looks like a oil change from my truck! i know that the benificials form a light brown snot like shit around the roots is this from the micro brew or have i got somethin bad ?
ph 5.9
ppm 300
room temp 73
rh 34
water temp unknown but kinda cold
cfl lights
plants look green and healthy(so far) with new growth some yellowing bottom leaves but are very bushy
i notice some black spots on the leaves of one or two
i kept domes on em a bit longer than normal
foliating daily with tap

does it smell bad? could just be the nutrients, I know that Humic Acid is blacker then a babies shit

no smell,under the slim the roots are white so i dont think its rot,im hopin its the mycors fightin some shit off,but as far as smell they smell pretty good actually humic ? is it being blocked you think?