Problems with Southeast Grow ?

I hope someone can lend some advice here. Some of my my budz put out three strains this year (Marocs and Haze crosses from Female Seeds (old FS.nl) and Ice Cream from Paradise. All were started late Feb to early March under 18 hrs of FL light. All were put out around 4/21 - 5/1. The problem is that they all started flowering by mid-late May. Most of each finished pretty good but they could have been much bigger if they did not start flowering almost right away when put outside. Should'nt these plants have just veged until at least 6/22 or so? Did we do something wrong? What can we do to make them veg longer next season?

In the past when growing indoors, our plants never began to flower until we cut the light to 12/12 but they were mostly clones. As for the few outdoor plants we planted in previous years, I don't remeber this happening but they were all bag seeds.

One more thing - all this years plants were from female / feminised seeds.

Thanks for any suggestions or advice.