Basically what you have done is something I too have done, on purpose, only I did it indoors.
The Marijuana plant has a life cycle of less than a year. It grows (veg), It produces buds (flower), then it dies, and all it can hope for is that it's genetics have been passed on for another generation.
But It didnt die, the environmental conditions were too good to kill it, so it figures, fuck it! May as well try to get more (if any) seeds out there so my species can thrive, so it goes back into a vegative state (if lighting and nutrients allow) then back into flower.
Now this has always tripped me out because on a plants second time through after the buds have been plucked off,the leaves and branches do just as you say, they look very odd?
All I can figure is that this could be a mutation caused by the plant going against it's natural life cycle, so I personally wouldnt use em' to produce seed stock (just to be safe), but they are definately worth keeping alive, and re-flowering.
And yes I have noticed a small drop in potency the couple of times that I re-veged plants, but it was still worth it.
peace