It seems it tries to fill an entire A4, as the image of the next page is too big. So it puts a lot of space between the paragraphs. But, I'd much rather have a big chunk of white at the bottom of the first page: as it looks now, it looks like there are stuff missing (for example figures).
Based on your given information I guess you are using a document class like
If you get a page break the text before will be balanced. A simple
The behaviour can be reproduced very simple if you are using the float specifier
So I recommend to use the specifiers