I decided a couple years ago to switch to mostly glass food storage containers. I buy them on sale and use them for left overs. They can go from fridge to freezer to microwave.

I still have plastic containers for storing bulk dry goods, such as flour and sugar.

I also use Mason jars for food storage.

You can put glass containers in the freezer as long as you leave enough room for expansion. If I am using a jar, I fill to an inch below where the top narrows, so there is lots of room for expansion.

If my plastic containers get the white scratch marks or discolored I toss them. I don't use them to store wet foods.

Same thing happens with some of my plastic storage containers. Going back to glass.

Having worked in hospitals for a number of years, there were MANY doctors who would seriously lecture if they saw someone using plastic (and that was after the BPA was removed). Glass is heavier, but it really is the safest, at least that's what I've been told. Now....having said that.....you can use lemon juice or baking soda to minimize discolorization.

This may sound old fashioned, but it was learned from my mom and her mom before her. I use mason jars (wide mouth) to store soups, chili, beans, spaghetti sauce in the fridge. (Before the empty nest, I even used them for the freezer.) First of all it economizes on space. The tall jars take a lot less room than a storage dish or container. Now as the for the stained plastic containers. Sometimes a soak in a mild bleach solution will do the trick, other times not.

I read this tip somewhere. When you empty a plastic container that has tomato sauce in it..pour Dawn or any dish detergent in and use a paper towel to wipe down before you use any water. I wipe the container with a dry paper towel first then add detergent then wipe again Let sit for a while then wash. Works on my splatter lit that I use in microwave too. For some reason if you use water first it doesn't work.

I use mason or large mouth mayo jars all the time for soup. Love them. But smaller amounts of veggies, etc., I use the glass storage containers.

The hard way is to use elbow grease along with something like Comet, Ajax or some other similar ABRASIVE cleanser.
For my homemakers that are young and or just don't know; elbow grease is using your hands and and other muscles to complete the task.
Those two cleansers I mentioned contain bleach as well.
Use something like a Chore Boy Golden Fleece scrubbing cloth and wet it just enough to turn the cleanser into a paste. That way the cleansing agents don't become diluted and weakened.
You'll probably have to scrub the dish a few times to completely be rid of the stain.
Now the easy but requiring a whole lot of patience way.
Use a soap and ammonia solution; HEAVY ON THE ammonia and let it soak for however long it takes to break up the color.
Usually, I go the abrasive cleanser and elbow grease route.
It doesn't take as much time or elbow grease as it sounds.
And in the future, might I suggest that you line you plastic containers with plastic wrap BEFORE putting in the chili or spaghetti with and or the sauce.
You'll still be able to reheat in the microwave in that container and just throw away the plastic wrap when the food is gone.