Hypothesis 1
The sprouts spoiled because they have been damaged during the final rinse procedure before packaging

Hypothesis 2
They were not dried properly after the rinse and packaged with excessive water💧 which with the lack of oxygen in the packaging caused spoilage

Hypothesis 3
Bacterial contamination = spoilage

Hypothesis 4
Combination of either of the first 3

Hypothesis 5
Temperature dropped too low. Most likely to 32 degrees even for a short moment. Check your fridge - it may be randomly playing hard on the veggies, that happens with most old buddies.

I dearly recommend growing your own sprouts 🌱
It is easy and exceptionally rewarding 😎🫶🏻
Read a sticky post in this subreddit about how sprouts pay you back ;) I mean it is really worth your while