Since the 1.12.1 update, I can't pour water over something without it lagging my game. I had a fountain that worked completely fine in 1.12 but, since the security update, every time a block of water "flows" it causes the game to freeze up until the water stops moving around.

I am using an Intel Core 2 Quad with 4GB of ram on Windows 7. My java version is up to date.