In the last few pictures you took, the camera is focusing on other items in the tank and not the actual fish. You can see this where the filter and hornwort are in focus and the fish is a little blurry. Digital cameras focus on big items first and struggle with smaller items, especially if they are moving. Make sure the fish is in the middle of the picture and give the camera a second to focus on it. Then click.
Keep taking pictures tho, it doesn't cost anything except recharging the camera. Go snap happy and take thousands, put them on your computer and delete most of them, maybe keep a couple that are tip top good.
After taking a set of photos on a digital camera, upload them to your pc and then format the memory card in the camera. If you take photos and delete some and keep some, take more and delete more, the memory card becomes fragmented and you can lose pictures. If you upload each set of pictures to a computer and then format the card after each photo shoot, the data on the memory card won't become fragmented and you won't lose images.
Formatting the memory card clears everything on it but also resets the gates in the chip inside the card.
Clearly have too much time on my hands but happy to blame @Back in the fold for starting the thread.
I wondered what would happen if I just dropped the underwater camera into the tank and left it running. Two perspectives, not particularly happy with either but I learnt enough to know what to do next time