having problem with flowering

well i ve been flowering now for about 2 1/2 weeks if not a little more im growing white widow in a aero system ph 5.8 ppm about 1000 the plants have been showing pre flowers for ever now..
i started them when they were 6 inches tall and now there like 2 1/2 feet tall and no buds and they are clones btw and these are the first clones that i have grown from this mother plant. so i dont know its habbits or anything like that so if some one could fill me in on whats going on or if they maybe just need a lil bit longer to start that would be great .its just i think they should have been well on their way to developing buds but ive been wrong before. thanks in advance ..

its hard to say with out some pictures, but you should have more then just preflowers in 2 1/2 weeks, are you in total darkness when the lights are off for 12 ?

yea their in total darkness when lights are out i dont know if a pic would really help or not theres really nuthing to see there showing preflowers and when i just went and looked at them it looked like they could be just starting to bud in spots but still no bud formation and i know i should atleast see clumps of hairs for being in this long.
ive never had this problem before thats why its pissing me off u think i should maybe decrease the light by a lil more and see what happens cause im ready to tear them up and start some diff clones but i will give them a lil longer i took a couple pics but u cant even tell if its budding or not