If any of your products can help me get rid of the yellow ring around my shirt collars, you have a customer (I hate throwing away $100 shirts after only a year of 2-3 times a month wearing).
Tip: get some rubber gloves to deal with the concentrated solution.
2) apply liberally a paste of baking soda & hydrogen peroxide to yellowed areas
3) let rest for 1-2 hours
4) wash normally
Bonus: use Bluette every few washes.