First thing - I am also an organic, T5, indoor grower.
When you vegged, how far away was the T5 from the plant?? It seems that they are that short, and are having some troubles, simply because they were so light starved during their veg stage. Now, trying to flower, there's just not enough juice to get them to really go.
Also, from what I have experienced and hear, is that you have to tack an extra week+ onto your flowering with T5's. The spectrum is just not as strong, so it's best to LST your plants with the light an inch or less from the plant canopy...keeping in mind that you want your canopy as even as possible so they don't grow into the lights.
Hope that helps...the HPS will wake those girls up, that's for sure.
Happy grow,
Smacks.