Pruning Question

My plants are 46 days old. They live their 17.5 hours days under under a 250w metal halide and 60w of fluros. One is 7 inches, another is 8, and the rest are all 5 or 6 inches. I don't know the sex of any yet and the room (3x3x7) is just starting to fill up (see pic).
The one that's 8 inches (possibly Blueberry) is the most vibrant. It's leaves reach up almost all day when I don't overwater. I think I should prune the top of this one so the lower branches can catch up and to keep the plant from getting any taller than the others.
The 2nd tallest is about 7 inches tall and at least 10 wide and is branching like mad. It gets tired before the others (after the lights have been on for about 14 hours). Not sure what kind it is. The pers who sold me the bag it came from asked if it's turning purple, and it is starting to get some color in the large fan leaves (see pic). It's darker and wider than any of the others. I'm thinking this one might benefit from some pruning, but I'm not sure if topping is the way to go.
I've never pruned plants before and I probably should have done it earlier (I want to transition to flowering in about 3 weeks, but space may force me to start sooner).
Any suggestions?? Thanks!

Ok, hopefully I'll get thi pics this time - still figuring out how this site works.

If you dont have to prune I wouldnt. I think plants are know what they are doing, and you will have a better yeild without. But their are mixed opinions on the matter.

Good looking grow so far mate, and goodluck with the rest <3

46 days old and 7 inches tall? My plants were 7 inches tall at 20 days of vegging on my last grow and that's vegging with CFL's.

Here's some better pics. Here's the one (possibly Blueberry) I'm thinking of topping. 8 inches last night.

Below is the indica that might want some kind of pruning. 7 inches last night.

And here's the room. Shorties were 5-6 inches last night.

doesn't look they need any pruning - you could top if you want - if that was part of your overall pruning strategy.

yeah dont just prune for no reason. They look pretty good.

If you want to try and get more top colas then perhaps try to FIM, but I would just let them be.