Thank you Dr King, but I am no pro. This is only my second round since high school in the 70s. LOL I just studied for 9 months before jumping in, then built a good room with a good environment and run good and easy nutrients to start out.
The strain is not purple. It's an OG Kush. I know many strains can turn purple with lower temps but was not aware of the color changing effects of CO2. Thank you for explaining that. On my first run my buds were no where near as huge as yours but they were similar in color. Great grow BTW! And I had problems keeping the room warm enough. So I was surprised they are turning purple at the tops. The lower bud leaves, 2nd & 3rd set from top, on some of the 12 plants are yellowing off and are easily pulled from the stem. This started in week 5. On the first round they stayed green till almost the very end. The only differences in this grow are Hortilux bulbs, CO2, warmer temps & Bud Candy added to the nutrient line up.