Cold weather will slow growth, but once it is warmer, growth should pick up speed. Growing at 12/12 from seed may have also played a part, the plants metabolism is most probably quite weirded out by that experience. Much better to grow at 18/6 during veg and have a normally functioning plant with a healthy metabolism and much faster growth in gneral. I am not sure why/how growing at 12/12 from seed would ever be a good idea.