Hmm ... I've grown them for many years and not had problems with them. It's possible that the shorter stems are because they are receiving more intense light than at the nursery where they were grown.
It's normal for a plant to have flowers in different stages of blooming, i.e. there will be some as unopened and partially opened buds; some will be fully opened flowers; and some will be spent and preparing to set seed. The spent floors should be removed, to encourage the formation of new buds, so the plant will be in bloom longer. Of course, you wouldn't remove the spent flowers if you wanted to try to save seed.
Remember that hybrid varieties don't usually produce viable seeds. Flowers that haven't been pollinated also won't produce seeds. If you do get viable seeds from your plants, the flowers will be different than those on the plants you initially purchased, because of cross pollination.
Be careful not to use a fertilizer with a high nitrogen content, because the plant will expend most of it's energy producing leaves, instead of flowers.
Does that information help at all?
"Isn't it enough to see that a garden is beautiful without having to believe that there are fairies at the bottom of it too?" - Douglas Adams