My first set I veged under a ufo like yours and i vegged for only 3 weeks under it before i flowered(trying to get feet wet) Now i have vegged 4 plants under an All blue UFO and they seem to grow a little faster but not that significant i would just wait until the plants are about 1/2 the size you want or so then flower them. i would leave them in veg from seed at least 4 weeks probably more like 6 for some decent size plants. the main thing is where i live Heat is a big problem when its 115 out side and your AC is just pushing to keep 79 or 80 degrees hps is almost not do able and cost so much just to keep your a/c where your plants can live. Check my log lots of pics on it. The other thing most notice with led's is you want to get all your buds to the top because led's have a little harder time penetrating. so fiming or topping maybe lst is recommended screen might work well (i topped one with my first grow much happier with topped plant than one i let grow wild).

well any way:stoned:

peace