Let us start off with two straight paragraph blocks to demonstrate the spacing between them.
The spacing both above this paragraph on the rendered page is as expected. No problems.
This is a two column block, split one third and two thirds.
Both columns are simple text .. nothing fancy at all. The space above this block on the rendered page is larger than the gap between the first two paragraph blocks.
Here is another paragraph block. The space between the columns block and this block is even larger than the gap above the columns block.
Here is another two column block, only this time we have an image on the left. The gap above this block is less than the gap above the first columns block.
Another paragraph block just to show the spacing between the blocks again. Once again, the gap below the columns block is large.