Why do frozen vegetables go bad more quickly after thawing than fresh cut ones?
Very simply; freezing breaks the cell walls.  

As ice takes up more space than water, as the vegetables freeze all the cells rupture.
Once defrosted, each cell is then little more than a slowly-leaking bag of nutrient, exposed to the open air. Whether or not any bacteria gets in &amp; starts to breed is almost irrelevant by this time, as your 'leaky bag' is going to dissolve into a pool of its own juices pretty quickly.

This is why frozen veg is cook-from-frozen not cook-from-thawed. An hour might be OK, a day is starting to get a bit much. By 5 days, I wouldn't do anything other than move it to the recycle using tongs.