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While bleach is a common laundry-whitening agent, it can react with certain kinds of fabrics and create a yellowish discoloration. It is especially important to avoid using bleach on wrinkle-resistant cotton, polyester, or polyester blends. Instead of trying to brighten up your white shirts with chlorine-based bleach, add 1 cup (about .25 liters) of lemon juice to your wash along with your regular detergent. Wash only white clothes with lemon juice, as it can cause colors to fade. If your white shirts are coming out of the wash with yellow or orange stains or discoloration, iron in your water may be the culprit. Get a home water-hardness testing kit at your local home supply store, or contact a certified water testing lab in your area and find out how to get a sample of your water tested for iron. If you live in the US, visit the EPA's water lab network website to find an accredited lab in your area: https://www.epa.gov/waterlabnetwork. Iron stains are very difficult to remove from clothing, so the best way to protect your white shirts is to treat your water. If your tests indicate that your water is high in iron, you may need to install a home water filter or water softening system designed to treat iron-rich water. If you are not comfortable installing your own water filter or softener, contact a professional plumber. Someone at a certified water testing lab in your area may be able to advise you on the best type of filtration system for your home.
Minimize your use of bleach. Use lemon juice as a bleach alternative. Check for iron in your water supply. Install a water filtration system if there is iron in your water.