Colour me all sorts of frustrated. I've done maybe a dozen or so grows before and had outstanding results. My setup is a two-level grow cab - flowering up top, mothers down below. All of my other grows in this cabinet arrangement have been indica variants, but this year I switched to a sativa dominant variant. My last indica grow in this box produced about 150 g. from about 2 sq ft. of screen - it's a small space, folks. I grow in bubbler systems and the flowering is done Scrog. I'm using Advanced Nutrients in both grows because I've had good results with them before. The mothers are under an array of Leds mounted to circuit boards - 1632 5mm Leds in blue and red. These are not the 12"X12" panels, but rather small circuit boards (six of them each board being 5½"X6¼" IIRC) with 272 5mm Leds soldered onto them. These are fixed onto a wooden frame, which is then suspended from the roof or the cab. This was my main light and I've gotten good results from it. It consumes 87w. But this year, I bought a new fixture for flowering and moved my original light down to the mothers. The flowering cab is using a 126w Led fixture which has four colours in it and is brighter - about 40w more and visually much brighter and more intense. It has 126 1w Leds and it is much more penetrating when compared to the 5mm LED unit. When I got this light, I did a side-by-side comparison with my 400w Hps. I took lumen readings at 6 inch intervals down from the light to the screen and at each level, I took readings in 3 inch steps in a circular pattern around the centre of the screen. The Hps was marginally brighter, but the readings were within the error range of the meter so I'm not ready to say that the Hps is brighter. I get about the same penetration downwards from the Led fixture, but that's not really an issue since I'm using the screen. Both cabs have light shielded intake and exhaust fans and I have good air movement in both cabs. I've checked both cabs for light leaks and found none. I check on them both twice daily and adjust pH as needed. Both grows are generally pH stable though I get some spikes in pH (~4.7 on the low side and ~6.5 on the high side) just after a nutrient change, but since I'm checking them frequently, these conditions don't last for long. Temps in the upper cab run ~72F and ~69F in the lower cab. The EC of the upper grow has been building (due to the nutrient schedule I use) and is at 2.18 right now. Now for the problem - the sativa plants just won't reach full flower. Hell, they barely produce any flowers! Twice now, I've placed rooted cuttings in the grow and they do fine. When I say they do fine, I mean that they produce copious leaves of good size and colour, the branching is good, the roots look healthy, the plants grow up into the screen and are spread out across the screen just fine. That is right up until I change the lights and from then on, they just slowly peter out. The new leaves that emerge get progressively smaller - my most recent leaves are about an inch, maybe an inch and a half across. That's down from the six inch fan leaves it was producing five weeks ago. I get a few scraggly flowers, but eventually the plant just sort of dies. The small leaves just turn brown and wither after 3 weeks or so. The first time through, I pulled the plant after 8 weeks because it was largely dead. I'm in the middle of a second trip down the same ugly path - this time I'm at 4 weeks in and it's doing the same thing. Last time, I got a handful of small flowers. This time, I've got one lonely little floret at each growing tip. Yep, one little floret. I'm so frustrated now that I've wasted three months on trying to get these silly plants to go into full bloom. I've grown sativa variants before, but not in this cabinet and not using Scrog. My last sativa grow was under that 400w Hps and that worked a treat. I've never had this much trouble just getting a frikkin' weed to do what it's supposed to do naturally. It's especially frustrating since I know I've gotten a very decent result with my indica grows with the same equipment. Sorry to ramble on, but I wanted to make sure I put as much information in here as I could. Anyone out there got any ideas? TIA Feadilcoy