First Grow Question On Flower Stretching

Hey everyone, seriously enjoying my first time growing its great. Im just over 4 weeks into veging with my 400watt MH in my tent. I have a Nirvana Masterkush(32 days old) Blue Mystic (29 days). Im growing in a tent thats probably 2x2x5. I want to utilize this space as best I can so im wondering about the stretching these girls will experience when the lights flip to 12/12. I have no experience what so ever and dont want to veg these too long if they will stretch out the tent. MasterKush I know should flower for 8-10 weeks and blue mystic a little bit more I think starting at 9-11. They are more kush dominate I beleive and right now are very bushy. I topped the Blue mystic once to get two tops then later topped to get 4 colas and removed two lower grow areas and placed them in cloning gel so there are 4 areas it looks like now on the blue mystic.
View attachment 2729959Blue as shit sits today.
Other side of blue, picture taken yesterday.

Now the MasterKush is a few days older and was topped just once with only dead leaves removed from the bottom up until today I removed two small grow areas and stuck in a cloning gel.
View attachment 2729962Masterkush today
Master Yesterday from backside.
View attachment 2729964

So main concern is when should I flower. Given the tent size 2x2x5 and room for two smallish fans when would you guys flip the lights. Any advice or critism is also appreciated, thanks

They are is Pro mix HP soil and being fed 1/4 dosage of veg nutes every watering which is every 3 times a week

Your plants are close to being sexually mature, mine typically show preflowers around 35 days. I then going into 12/12 at any time, but invariably wait for 40+ days. In any case, they don't look too tall, quite bushy, so you should be fine in that 5' tall tent. My advice would be to continue to use the MH during the stretch phase of 12/12, it will really do wonders to control the height. Once stretch slows down, you can switch to HPS if that is your plan.

I was thinking of just slowly progressing to 12/12 with my timer over a week period. Thursday they will be 5 weeks so maybe start adding an hour each night of darkness with the MH bulb then by week six they will be at 12/12. Iv read around and people are saying MH is great to control stretching but because they are so bushy and short is that really a concern for me? Does HPS bulb make a huge difference during the first two weeks of flower.

HPS is more red than blue, MH is typically opposite. You want blue for vegging, and the first few days/weeks of 12/12 is basically still vegging, because the plant is still packing on stem and leaf structure. Once stretch has slowed and pistils show, then the plant focuses on budding/flowering, that is when you need that extra red from the HPS. So really, no benefit from having the HPS during the beginning period of 12/12.

cool good to know thank you, if MH can control stretching im contemplating veging another week or so