I can't remember how I first got pink lilies, but what I've been doing recently is placing the red and white lilies in a diamond shape, with a jacob's ladder in the middle. I don't even use any fertilizer, and I get 2 pink lilies just from these four flowers! Honestly, it might just be luck? Well, you might already place your flowers like this but maybe it might help. i honestly get more pink lilies with this than white or red.
—-X—-
x—o—x
—-X—-
capital X's could be either white or red, with the lowercase x's being the remaining color. o is the jacob's ladder.