Short Tail Fin? Will It Grow?

[AlitaConejita]

Hi all,
 
I was looking at bettas at my local petstore yesterday and then at images of crowntail bettas (just googled it: https/www.google.com/search?q=crowntail+betta&source=lnms&tbm=isch&sa=X&ei=tBuBUoLYJcOzsATRq4Fg&ved=0CAcQ_AUoAQ&biw=1366&bih=634) and I realized that my betta's tail fin is no where near as big/long as those in the google images or the other CTs at the petshop.
 
I don't remember thinking before that his tail fin was short ... may-be it has gotten shorter?
first pic (Early August):

 
Pic from today (Early November):

 
Either way, will it grow as long as the tail fin of the other crowntail bettas in the pictures, or is there an extra long tail fin gene or something that Jack just doesn't have?

 

[Wildbetta]

With the damage that Jack's fins have had there is no guarantee how much they will fully grow back out.

 

[AlitaConejita]

Bummer

Is there anything I can do to promote growth?