@invisiblgirl, I got my snowdrops to perfect without an issue not that long ago, at the same time I was working on every other plant. Will say that it seemed like some plants go up faster than others...but with plants regularly going active/inactive with seasons it's so hard to tell for sure. I guess if you have them ALL in a greenhouse it'd be easy, but I didn't and was manually rotated plants inside and out.
Stick with it, it will get there. Switch to using fish with a higher value (Salmon or Tuna work great) if you want it to go faster. They are both much better fertilizers then growfruit. I just bought the fish I used when getting the sim garden up..mostly I used growfruit and pomegranate, like you are, but I did buy fish to use for the slower-developing plants.
For me, at least, it seemed to be some of the flowers that were slowest to gain quality, and snowdrop is a flower, so it may be a good candidate for fishy-fertilizer for you.
Good luck!