I put garlic and Marycn to cure Betta with epsom salt...?

this morning and when I came back in the afternoon he was gone!!!!!!!!!!!!!!!!!!!!! :(:(:(!!!! He was at the bottom of the tank not eating, swollen and his scales were up. His mouth was white and cottony. I tried to save him and separated him from other fish. I put a few strands of very thin garlic in the tank. He had just one night with the maracyn. Is it my fault??? I'm so sad!!! He was at the bottom of the tank and looked like he had trouble breathing and wasn't eating. Wh.en I put garlic, he actually swam up but then stood at the bottom. He was like that since last night. I feel horrible