No man, sexual maturity doesnt mean the plant wont flower. I sex plants at two weeks old and they spit pistals in ten days. Guys also run 12/12 from seed all the time and they flower. Im thinking genetics probably. Some are quick outta the gate, some arent. The good news is that they all flower something but then again its not always spectacular what you get if its not a quick horse outta the gate.
As for the suggestion of the canna pk boost, i use all those products currently and i thoight that the pk boost wasnt supposed to be used until the fourth week or later in flower. They reccomend useing the vega for the first week or two i think also. I dont have the feed chart with me but like i said im my earlier post, i do run veg nutes for the first while in flower, four weeks sometimes five depending on how green theyre staying. But as i progress i add a little pk boosters to break them into flowering nutes slowly.
How are they doing these days? Got flowers yet?