Leveling Travel trailer

Since it is already on blocks, I'd would just use a jack or two or three. Move all of one side fairly evenly. I used a five gallon bucket full of water and a clear hose to level mine. Push the hose I the bucket starting at one end (secure one end in the bucket with a rock). Push the entire hose in the bucket, ensuring no air bubbles are in the hose. Put your thumb on the hose and pull the none secured end of the hose out of the bucket. Keep that end higher than the water level. Ensure you don't spill any water. Hold the hose next to the frame which is the correct height. Adjust water level so the water level is the same as the frame. Then use the hose to ensure your trailer frame is level when you make your adjustments.

The fact that one side sank could be a good indication you should add another peer, or you need to increase the surface size of the bottom block of your existing peers.