Topping

Atleast the very bottom red line. And what are you growing with? light source?

the light looks descent due to the closeness of the nodes. more importantly, if you were to top them there, you would slow down if not stop vertical growth all together(short and bushy). first of all, depending on the strain, 4-6 weeks is common starting point to start manicuring/training plants from seed. clones, being as old as their mother, can be trained as soon as new growth and node formations appear. now, i would suggest using the FIM technique. to do this simply take a pair of nail clippers and snip half way down the top bud/node formation. new node formations have multiple node points bunched together that are sometimes refered to as buds. doing this will result in 2-8 new branch formations from that are centrally located at the cut point. then you can repeat the process when she gets bigger. while feeding high N fert like a 20-5-5 keeping the P and K even. this will give you crazy results and is a must for strains like bluebeery. aloha

FAQ has lots of info on this subject and pics too.

light source is 400 watt MH, and i have 3 strains growing... White Widow, Northern Lights X Big Bud, and Magic Bud

Hmmm I cut right above the node I want it to split at as the next node up is forming.

before putting my outdoor sativas in the ground i top them once while under the light so there is two main colas as upposed to one. i've had one get sooo big one year! the main "trunk" was the size of my ankle and each main "Y" branches were the size of my wrist. i think it depends on strains it takes alot of expierimentation. some will yield alot more by not doing any cropping at all.

Thanks for all the replies, they were helpful, although it leads me to another question: The soil im using is foxfarm. The guy who sold it to me said i dont need any nutes, everything i needed was allready in it. Here is the description of the soil.
Ocean Forest® Potting Soil
Good Things From the Earth and Sea
The ultimate potting soil—everything your plants need, in one bag. Ocean Forest® is a powerhouse blend of premium earthworm castings, bat guano, and Pacific Northwest sea-going fish and crab meal. Composted forest humus, sandy loam, and sphagnum peat moss give Ocean Forest® its light, aerated texture. Start with Ocean Forest® and watch your plants come alive!
Garden tip: Perfect for containers and ready to use right out of the bag. Ocean Forest® is pH adjusted at 6.3 to 6.8 to allow for optimum fertilizer uptake. There’s no need for nitrogen fertilizers at first; instead try an organic blend like FoxFarm Big Bloom™ Liquid Plant Food to encourage strong branching and a sturdy, healthy growth habit.

Even there, it says there is no need for high N ferts. So, should i not use high N fertilizer with this soil, or do i need it for the topping process? I topped them 3 days ago at the lowest line on the pic, and i havent seen much growth yet, but i suspect this is normal. Please post back so i know what to give them. Thanks again for the help.

Before bothering to top and take all the clones Id suggest you let the plant hit about 10 inches then pull 1 clone from each plant and label it to correspond with the plant it came from. Next take the clones get them rooted about 7-10 days then toss them right into 12/12.I about 3-7 days the clones will show sex and you then match the females to the parent and you know which plant is a female and good for clones.The parent will be about 12-14 inches then top it back to 10 inches and kill the males that gave male clones. Early sex and intime to top and you know your having a female mom to keep for clones.