Runts

I have a collection of Mbuna fry, from 6 or seven different spawnings.
about 25 total. The largest have grown to about an inch and a half. Even
the largest from the latest breeding have reached an inch. There are 3
little fish, however that refuse to grow. I've watch closely at feeding
time for the last few weeks, and they seem to be eating more than enough,
yet they're still only 1/2" long. I have WAY too many of them crammed into
a 20 gal tank, I know. I was hoping to see some adult coloring before I
take them down to the LFS. Their Father was M. estherae, and I Think their
mother was G. acei. The original fry is about 3" now, and a very pale ,
almost albino, pink. He has thin, blue "eyeshadow". The others seem to be
following the same trend.

Anyway, are runts common, or could other conditions be affecting their
growth?


P.S. I can't say for certain if these 'runts' were from the last breeding,
but it might be worth mentioning that the mother died within weeks of giving
birth, and the father about a month and a half later.