Fps super low

When I played MC (18w15a) today, my fps has been low ever since the snapshot came out. I'm using a dual monitor (thats why its a strange resolution) with both monitors supporting 1280x1024 @75 hz. If I play MC on lowest quality, it is capped at 75 hz while not using vsync. When i switch to my usual settings (16 chunks, mipmapping, biome blend, smooth lightning etc) it is on 30 - 40 fps. In the snapshot before this one i got 60 - 180 fps with these settings. I am playing without any packs or such. Anyone an solution or is this a world loading issue?