brown roots cut or let stay

I do this way to often and no reason why but I do over feed or something else but whatever I do now and then Ill have brown roots and I was wondering if I should cut them off and let all the nice white ones keep it alive or leave them. I just dont know if the brown dead looking roots are doing any good or not any thoughts would be great.

what is your water temps? brown roots are never good. is light getting into your tank? nice strong white roots that grow out of control is what your looking for. if not this may be root rot, does the water tank smell like a sewer? slimey and nasty? or do you think its from your nutrients?