In general, your subject matter is too centered. You’ll get better images if you apply the rule of thirds. A Google search will give you plenty of examples, but basically you divide the frame into thirds and place the main object of your image at the cross points or along the lines that divide the frame.
Below are your shots followed by my adjustments to show you what I’m talking about in my commentary.
This image is an example of not deciding what you want to show. Do you want the viewer to see the mushrooms, the zoanthids, or both? Regardless, the majority of your image is rock and that overwhelms the mushrooms and zoanthids. The image is also over exposed, with many hot/blown out areas.
Your first step is to fill the frame with the subject matter and eliminate all of the rock that is contributing nothing to the image. When you do that, you’ll eliminate all of the light and dark areas that are fooling your camera sensor and will get a better exposure on your subject matter. Also, try bracketing your shots, shooting one shot that is one stop overexposed, one that is at the settings indicated by the meter, and one that is one stop underexposed. Then you’ll be able to choose the best shot that eliminates blown areas.
You can see the difference in my version in which I crop out the extraneous matter and put the zoanthids and mushrooms on thirds. Now the animals dominate the frame and show the viewer what you want him/her to see. It would be a better image if you choose one or the other to show.
This second image is the standout of the bunch. You have good exposure on the subject matter and relatively few blown areas. In your version, the colony is too centered and there is too much rock shown around the colony. In my version, I made some levels adjustments to bring out more of the color and improve the contrast. Some sharpening brought out the detail. Again, an tighter crop fills the frame with the colony and puts the bulk of it on the upper and right thirds.
This shot is very overexposed because your meter was fooled by the large dark areas, causing it to blow out the hot areas. If you fill the frame with the colony you’ll get a better meter reading. Underexposing by a stop will also help. It also looks like your white balance is off. In my version, I cropped tighter and tried to make some adjustments to bring out color, open shadows, and bring down the highlights so they aren’t so glaring. I had limited success, but you get the idea. I also moved the colony off center to help the composition.