If you have a silver or golden watering can, water the hybrids everyday and they should pop up more often. c:
Also, Jacob's Ladders will help too when you plant them by the hybrids.
Fertiliser, diagonal planting, and nature witchery. I mean, er, Beautiful Town, to encourage villagers to chip in to the watering chore. Their assistance is why I have all the blue roses I do.
I actually had trouble breeding tulips for the longest time until I lined them up horizontal. I normally do diagonal and that worked fine with roses but either some flowers are different or I have weird luck, either way maybe try changing up your methods if things aren't working and see if it helps.
Oddly, fertilizer doesn't work for me. I once used fertilizer on a patch of orange roses to try to get purple, next day, only common flowers. Then I just water them normally, next day BAM 4 purple tulips!
I dunno if maybe the fertilizer takes a few days to kick in or it just don't work for me??
1)Golden watering can
2)Fertilizer
3)Fertilizer
4)Did I mention fertilizer...
5)Jacob ladders too if you can buy them from someone(If you didn't get them already)