I think time travelling has something to do with the number of hybrids. I don't time travel and I have a few. I use the checkerboard pattern, which is exactly what it sounds like. Imagine a chess board in your town, and plant your flowers on every 'white space'. Every morning, remove any flowers that spawned on a 'black space'. If you're making fields of the same type of flower this way, you'll probably get more hybrids.
I find if I have 2 white roses and 1 purple rose I will only water the purple and I find it works very well c: So I suggest only watering the hybrids:3