well, tomato is higher in Sugar than most veggies ( well it is technically a fruit) so those who are really ill might want to avoid it. Also, as with anything premade , mold might be a concern...might. You did not mention what the spaghetti was made from. Wheat is bad , but white flour is worse and rye is really bad. So I would be curious there. What you could do with the the tomato sauce is try only a little and see if you are okay. I don't know how far along you are with candida, but just so you are aware, it is actually recommended that one stay on the diet for at least a few months after you are well to ensure it does not return on you. So becareful. Also yuo might be able to handle brown rice...the slow cook kind and put some tomato and basil on it and eat like spaghetti.
Don't feel bad , I am on over a year on the diet and counting. Learned the lesson that diet alone will not work the hard way.