Im not sure you understand how color temp works with LEDS wether its 3000K or 6000K 99% of cobs are based on 440-460nm blue chips, they do not put out UVA or Violet light. and the blue spectrum starts at 400nm visible Violet light IS BLUE LIGHT and infact the 400-440nm is the most beneficial blue region for photosynthesis once you get past around 460-480nm photosynthesis starts to take a bit of a dive. If cobs put out Violet light (not Ultraviolet) that would be awesome in my books, violet is the often missing spectrum perhaps its not as efficient in generating photons for photosynthesis as blue, but for quality a full spectrum at both the red and blue side is important. however some cobs, like the luxeon crispwhite use both violet and blue chips even though they barely get 100 lm/w this is mostly due do the fact that its a high cri with lots of deep reds and half the chips are 410nm violet wich is barely visible thus barely contributes to any lumens. its actual PAR efficiency is probably pretty good and they would definitely make your grow room POP with colors as these cobs were designed for art galleries that brings out some really vivid colors and true whites (perfect for showing off the trichome and purps action)
These plants were done on twin vero 29' retrofitted to run on a single driver per cob in the shell of a rolandro 400 watt cob setup from ebay that burned out the LEDs really fast. I find that stretch is strain related. All these plants were started the same time and they are different strains. the tall ones are Purple pineapple express, short one is mendo purps, medium one in the forefront is Lime green skunk. I been doing this with cobs 2 years and cfls 2 years before that. This is my most successful grow yet on the Vero 29s. 4 month veg time 3000 k 90 cri