Fruits and vegetable in C4 are very poor quality. The best are in Giant/Hyatt Plaza (not everywhere!), then there are Megamart, Shoprite, Family Food (Airport). All these are not exceptional but better than the average in Doha.
Approx. 2 years ago in C4 CityCenter (if I remeber well) meat dept. was closed for several months for same problem - unhygenic situation.