Game and Redstone Tick speed abnormally low

I've noticed any redstone creations were taking a really long time, and couldn't figure out why until I saw a repeater. 4 Ticks was taking an entire second, not just 0.4 seconds. I then spawned a chicken and saw that it wasn't just redstone, the entire game was only running at 40% speed, despite the FPS hovering around 65. I tried changing my settings to minimum, as in 2 chunk render, no particles, no clouds, no mipmapping, fast graphics, but there is no improvement. Anything that requires precise redstone timing is broken, and survival is worthless.