Hey Growmie,
Yes, 6-8 inches is way too close, even most companies recommend it being higher, for a plant this age I would raise the light to about 18" to 24" inches above the canopy, If you keep it this close you're definitely going have some heat/light stress going on. Feel free to shoot me a holler if you ever need any help, I'd be honored to assist you. Hopefully, this was helpful, and remember ... "Happy Growing" and "Free your mind one puff at a time".