Hmm, really wonder what the yellow-ish one will look like in next few weeks. I guess you have them all in the same environment, so it should be genetics, right?
@Butrus, 2 of them were yellow on week 1, one has come right by itself so far, gonna start feeding soon soon so hopefully it will go away. I also havent been using cal mag as I soaked the medium with cal mag and water, but am thinking theres 'not enough of it present.