Stunted Boeseami Rainbows?

[Mikaila31]

I breed my boeseami rainbows about a year ago. I collected about 50 eggs total and had about 40 hatch. (It was my first time breeding anything besides mollys) At the moment I have 5 left, most died at about the 4 week mark. They have been living in a 20gal high there whole life and at the moment the are only 4cm long. Is this the right size they should be at this age? When they were first born I fed them vinager eels, then microworms, and grindal worms. Now they eat flake food and bloodworms, but they always seem small for being a year old.

Edit*
A quick pic of them

Thanks,
Mikaila31