Will need some more info if you want answers.
- What size is your spawning tank?
- What size is your grow out tank?
- How often did you change the water?
- Did you have live plants in any of these tanks?
- If so, what species of plants.
- What foods have you fed the fry?
Photos would be helpful too.
Are all of your bettas still in the same tank?
Largest juvie from my spawn in mid October 2012 is at least 4cms.