You should get amazing buds from plants that are 2 feet high when put into flower, IF you have the lighting to flower them properly, which seems unlikely since you are a beginner. (See next paragraph.) What you receive in yield will be totally dependent on the lighting you use now (during bloom), assumming everything else is done correctly.
Those plants will probably hit 6 feet (or more [strain and light dependant] - sativas can easily hit 4 times their vegged height) during bloom because you waited so long in veg - growing them to 2 feet ... this is one of the biggest mistakes I see with beginners at RIU, i.e., growing big plants before putting them into flower when they don't have the lighting to cover a plant that big properly. (If you've got the lighting, great, if not - waste of time.) I see posts over and over again ... "is this plant ready to go into flower?" Fact is, you can flower whenever you want. For example, I put my plants into bloom at 6 inches and I'm using 2 x 1000w HIDs. I do use the sea of green (SOG) method though, so you'd probably want to grow them bigger than that. Regardless, the point is to grow them to a height that is suitable for your setup then put them into bloom. You don't need to wait a certain length of time or until the plant looks like this or that - just grow to a height that your setup can handle given the fact that they may triple in height during flowering. (The less light you have the taller they will be when finished. For example, with 2 x 1000w lights my plants still double in height, or even more depending on strain.)
Yes, cannabis plants can start flowering on their own; maybe that is what is happening to you, I certainly don't know by that one post. If they are left too long in veg sometimes they will start to flower - sort of like being outside. Sometimes they just start to flower for no apparent reason but this is quite rare.
In the future remember that growing a larger plant before blooming will not help much with yield unless you have the lighting to compensate for that. Why? Because the good fat buds will only develop within the range of efficiency of your lighting. You may get some extra 'popcorn' buds, but you also spent a lot more time in veg.
Please note that the above is a very general explanation. There are so many variables I could include it would take a novel to explain all the possibilities. I do hope it helps you in some way though. Good luck to you.
