Water is killing grass very quickly

I've been using water-powered flower farms, and I notice that water will turn certain grass blocks to dirt very quickly. I remember using this farm in earlier snapshots with no problem, but now, after even a few cycles, a number of my grass blocks turn to dirt. I tried to reproduce this by dropping a water bucket onto grass, and within seconds, several grass blocks had turned to dirt.

I tried this during daytime and nighttime. I lit up my flower farms. I've tinkered with the tick speed, but this is happening at tick speed 3.

Please help.