I planted a variety of zinnias this year....smoothies and candy cane colors, which are said on the packet to grow large heads aprroxiamately 4 to 6 inches wide, but my largest are onlylike 2 inches at the most. Why havent they grown big...I was thinking maybe did I keep them too close together so they wont get big? I never divided them apart. Just let them grow in masses together.