I can't take the bedrock lag anymore!

My computer runs on a solid 150 fps while playing Minecraft, and recently, I've been making a CTM map, or Super Hostile. When i first started expanding the bedrock ceiling, I experienced no issues, but now that it is bigger, when I place down bedrock, my fps goes anywhere from 120 to 10 fps. If you can't open these pictures, please believe me. This has been happening for multiple versions and I just really want to make a map without so much lag.
-Darkclaw234