How big are they currently? I have two azureus that are currently about 3-4 months out of the water, and I have to say that I thought they grew pretty quickly (not as fast as my tincs, like Bill said, but they have grown noticeably).
I have found that you can easily get a growth spurt out of these guys by switching to hydei once they are big enough to take them. They can quickly gorge themselves on these big, meaty, slow moving flies (and there should be a higher ratio of nutrients to chitin in hydei). Another nice thing about being able to use the hydei is that the size of their wings allows more vitamin powder to stick to each one.
Be sure you are dusting every day if you are not noticing growth (I dust every day with a Rep-Cal/Herptivite mix for all my frogs). This could be a sign of Calcium/D3 deficiency, and could be caused by a calcium supplement in a form which is less than ideal.
-----
Homer W. Faucett III, esq.
Purveyor of Trivialities and Fine Nonsense