Grand Daddy Purp Flowers Developing Slowly

My Grand Daddy Purp has been a slow growing bushy plant, very thick. My problem is my GDP has been under 600 W Sodium for 4 weeks and the flowers are small. They got to a certain point and seemed to stop growing. We put in 12/12 after 15 weeks of veg.
It is under 600 W Sodium 12/12. Using Flora Series with Liquid Kool Bloom. Using the prescribed amounts for aggressive growth. Leaf edges are starting to yellow showing nitro deficancy.
When I inspect the flowers with a 100X micro it has short trichones but very very dense.
My questions is this type of growth pattern normal?

some pf the purple strains like erkle and this one i noticed tend to veg slower than other strains i grow....i vegged mine for 8 weeks and they were about the same size as my 5 -6 week old Deep Chunk hybrids

Thanks for your response. The thing that really excites me is the desity of the trichones. Just transplanted two GDP clones from another plant and it took them 3 weeks to develop visable (thru the clone plug)roots when my other strians are taking 2 weeks. Hope its worth the wait.