If you use frozen fish food for the tank, if it smell bad, don't use it. Animal with a brain (fishes, shrimps) often spit bad food out. Scavenger can utilize spoiled food, but brainless animals (anemones) will ingest things according to chemical stimuli and will take in spoiled food and get infected and will not do well with a spoiled meal. Sometime they recover, other time they don't. Siverside and krill frozen with gut intact will spoil quickly if thaw out. I know that may LFS and wholesaler will just refreeze thaw out fish food then sell them. This is a huge no-no with human food.
IMO, feeding anemones with krill and silverside or other frozen fish food is like playing Russian roulette with their lives. You will never know which feeding is going to be their last feeding. This just my opinion after loosing a anemone and spend time thinking about it for a while trying to decide why I lost that healthy thriving H. magnifica