Is it OK to use expired fish meds??

Thanks all, I would agree with the antibiotics not being as powerful & making stronger bacteria. Just wanted to make sure if the opposite would happen like them going bad & having a negative effect on the fish. I did mix up a batch of Maracyn 1 & let me tell you in the mixing glass that stuff smells really, really strong. I did not re dose or use #1. I dumped it in the garbage. I am still seeking med #2 . The one that works on gram negative. It could just be that my fish are getting old but I am not really sure what happens when fish get really old & start dying from normal end of life cause verse an actual bacterial infection? Could there eyes get distorted a little before they die of old age?? Sounds stupid but really old people do not look to good when they are very old, so maybe the same thing happens to fish, maybe someone can give advice on this. Do fish look good until their last few days or do they gradually begin to break down an not look so good before they die?

I am going to feed them some baby brine shrimp to see if it helps their vitality. They have been getting pretty thin for a while now. They still eat well with flake food but I have always felt they needed more verity. I cannot get back to regular water changes until I am done with the meds.