When you say SVL. I am assuming you mean that. So the total lenght would be around, 13 to 15 inches. Then I have to ask, what makes you think thats small for their age? I would think thats fine for the age you quote.
Also, I have to wonder, considering your experience, why do you think you can do better?
I also wonder, what size do you think they should be and why?
Then your post leads me to wonder about something else, whats the difference between a petshop ackie, and any other ackie?
It seems you want to insinuate that petshops automatically take poor care. While many do, many many reptiles are mistreated in private hands. In fact, many here.
I think you may have mammals confused with reptiles. The design of reptiles is to coast(exsist) thru poor times, and then progress after they pass(if they live). Consider, this is normal in nature.
A better question would be, could an individual that has had poor support, whether its from you, a petshop or nature, reach maximum size? average size, or could it attain normal life events at a relatively small size? My guess would be, no to the first, and yes to the second and third. FR