3rd grow CFL OG18 and NL#5

Sup guys -

My second grow consists of 1 dinafem white widow, 1 paradise delahaze, and 2 nirvana northern lights #5 in 5 gallon smartpots using fox farms soil and nutes. They are under 14 23w cfls - 12 2700k and 2 5700k for 12/12 flowering. They get watering/feed around every three or 4 days, and usually end up using about a gallon or so of r/0 water for each plant. They are 5 weeks into flower and I am starting to see alotta of brown hairs...should I start the nute flush? I may just be getting anxious to smoke some of these ladies, but to me they seem like they are nearing harvest time....maybe another 2-3 weeks I'm guessing. Any thoughts about this or comments about my grow?