I have a Florida Red Belly who is acting strange. When I go to feed him he acts interested but will tilt his head all the way back and appears disoriented. He spins in circles and will almost flip upside down. His eyes are clear, his nose is clear of mucus, and he isn't gaping. He is alert and and full of energy. Most of my research suggests internal bleeding or resp infection,

I recently changed his aquarium from a 75 gallon deep water to 75 gallon shallow water for aquarium design and water quality purposes.

He is approximately 3 years old. All other turtles in the enclosure are fine and the apparent sick turtle has be placed in a dry enclosure for now to isolate him. What is going on? Is a vet immediately needed...taking him the vet is not an issue just want to know what you all know. Thank you.