in 4 weeks your plant may be over due, and the thc will have broken down to an amount that decreases your potency substantially. if it's higher sativa maybe not, i let my widow go 10 weeks and and on the very last day i saw my mostly cloudy, 1-2 amber triches here n there. you should not judge a harvest by the pistills at all. always check the trichomes, trust me. pistills are very innaccurate. the plant flowers in the same amount of time under a hid or a cfl, so the argument of cfls taking longer is probobly not true. cfls shoulf be kept within 1 inch and tweaks twice daily for optimal results, small cfl leaf burns if they touch are worth the risk in the outcome, ask Garden Knowm.
if your plants are 7 weeks into 12/12, you need to get a pocket magnifier from radio shack, and look at your trichomes under 100x mag. cloudy opaque trichomes are peak potency.