Yesterday, I accidentally overfed my Betta fish. Today Is saw the water was murky, so I changed it. Now my fish just stays low at the bottom, and only moves to breath from the top. What did I do wrong?! Can someone please help?

Hi, We had left the house for a few minutes, with my betta's hood on and secure, and left him on my drawers with my sweet dog and scaredy cat fast asleep. However, when we came back, i walked into my room to find the fish tank knocked over and all the contents in one of my drawers. The cat had...