I use a BlueLab, it's just not super accurate. It bounces between numbers a lot, so I sometimes have to estimate. At 75% of Lucas, I read at 910 (an average of the 2 readings). I was estimating 50% Lucas because I wasn't sure since I hadn't done it yet. I'm guessing that I shouldn't continue to have problems with such a low PPM now. As for age, I flipped to 12/12 at 4 weeks, but the clone is much older. I also "walked" up to 1200, by going with 50% the first week, and 75% the second week of flower. Was that too fast? I have limited space in the cab, so I flip to flower fairly early....