Try flipping the first two horizontally. Since the majority of the world reads from left to right, our eyes tend to look at an image from left to right. Right now they are facing more to the right and it doesn't connect as much. The composition now tends to lead the viewer off the page at the lower right since the fish is looking that way and the thing it's on. If it's looking to the left the viewers eyes will stop at the fish and keep them looking rather than leading on to the next image. There are instances where you would want to lead the viewer to the next image though.
First image - Flip Horizontally, Darken background
Second - Flip, lighten the fish and only slightly darken the background
Third - The lighter part of the image behind the fish is distracting and makes it hard to see the primary subject. Darken that area to even out more. Then darken the background and lighten the fish.
I put together a basic example of what I'm suggesting and obviously it could be adjusted a little more but this should give you the idea.


