Flowering out of season

I have 4 outdoor plants all 2 months old and over 29". They have all been growing at a consistant rate, but about 10 days ago one stoped developing leaves and started making little white hairs on each node. I know its flowering but i dont understand why when its in 13.5 hours of light.... is this common for them to flower out of season or is there something i did wrong. the other 3 are now about 5" taller than it now and showing no signs of flowering.

some strains have different light requirements when it comes to flowering, i heard. not too sure. as for the other ones not flowering, either they're different strains or they're just same genotype with varying phenotypes. maybe the one thats flowering is just "different".