53.64 in the 100 LCM Free Finals

After some food and a 2 hour nap, I thought I would be ready to swim finals. Looks like I was wrong. I took out my 100 free in a 25.20, slightly slower than the morning but not a dealbreaker regarding a good time. I fell apart on the way home, worse than usual. I touched in a 53.64 which was four tenths slower than my morning swim. I took last place in my heat. I went from 21st to 24th place, sort of disappointing. I chose to scratch the 100 fly this evening. I'm just not feeling it.