Second Grow Questions

Second grow 3 plants with soil, soil mixed same as the last grow but for this grow I'm using 400 watt 5200k mh for vegging and my plants after 3 weeks leave me with a 5" high plant. Last grow I used 6 42 watt 6500k cfl's and my plants were over 12 inches in the same time. I was wondering if I need to supplement my lights with a higher spectrum or maybe my mh is to close to the plants, its about 16 inches away.Can't really get it closer because of heat. I'm growing in a 2 x 2 x 6 foot high cabinet. Ventilation is good with two fans blowing at the plants and a 4" inline exhausting.Any ideas?

Pics? How many nodes? Using a hid light escpecially mh will encourage tight internode spacing. Your plants will stay much shorter than if you were using cfl. Is it otherwise healthy. Indica dominant? Post some pics.

And I assume you meant 52,000k

Its Caramelicious as a strain. I just changed my bulb to my hps and the plants have grown over a inch. I vegged at 18-6 for a month , switched to 12 12 two days ago. Interested to see how rapid the plant grows. I'm going to inject C02 at the base during the dark phase. Did the same during the last week of vegging and all it did was make the leaves a bit darker. Have the hps about 12 inches away and it seems the plant tops are stretching a bit just in one day. I'm enclosing a couple of pics but otherwise the plants seem healthy
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Plants are 8 weeks now, been flowering for the last four . Lots of buds starting everywhere. I was wondering if anyone had experience on how long this strain before harvest on a average, I heard 8 weeks flowering.