If I take a dead snail out of it shell will the empty shell realise anything bad?

I had 2 turbo snails that died. I am not sure of what there may not have been enough food, I'm still getting more live rock but I have a long black spiked sea urchin that eats as much as it can all day and night so might not have left a lot or it may be to do with high nitrates what I am still struggling to get down. So my snails died and the crabs were not that interested but they were definitely dead they stank!! So i managed to scoop them out after a lot of effort but could there be anything still rotting in there? Or are they good to keep for when my crabs get bigger?