I did this before. every flower looked like this:
The whole quilt looked like this:
I bought turkey red fabric that looked similar to what degraded and needle turn -appliqued it over top of the degraded flower petals. It turned out perfect. It was not hard.
If it happened in the middle of the white, I may have covered the spot with tulle and darned it, but i would never encase the whole quilt in tulle.