Was the light as far up as it could go the whole time? If so, it was probably too far away and caused all that stretch. Not a big deal... get some string, tie down the tallest branches. (they will bend, I doubt those stems are very woody) Do not cut anything if it has started to flower. If you do not have room to tie them down because its already over crowded and you can not make the space bigger.... it might be worth it to sacrifice a plant or two to make room for the rest to properly flower.
How long have they been showing white pistils? this will give you an idea of how much more they are going to grow. If the seeds came from a bag of mids... they will stretch a lot no matter what you do (maybe not that much tho)
Do you keep a fan running on the plants? How big is your grow space? If the space is too crowded, the heat from the light will cause the humidity to rise and with no extra fan moving things around, mold would naturally develop.