Running a GLR veg some strains like OG Kush, Blue God and Kushage all flowered. These same strains flowered under 16/8 but not 18/6. This is personal experience.
What type of light are you using? I've used GLR with about 6 different varieties of OG kush and haven't had any issues with flowering or showing preflowering under GLR...not knocking your experience, just would like to know more about the varibles involved. You flower with 16/8 lighting?