Hello, as explained by you it gives an idea that there is a gap between the crowns and the food is getting stuck which is causing the foul smell. Ideally get the crowns changed because no filling is going to solve the problem. And also get a round of proper cleaning in that particular area specially.
Thanks
Next Steps
visit a dentist, get a round of cleaning done and get the crown changed
Health Tips
for time being use lukewarm water and salt rinses