Silicone utensils are changing the taste of my egg whites
Assuming that your spatula and cookware is completely clean of any residual food, I strongly suspect that cooking spray is your issue. If I'm cooking something very bland (like egg white) I won't use cooking sprays for exactly that reason - I taste it too. Do you have a microwave? You may not need any oil at all, although scrambled egg (or egg white) in a microwave without oil can actually be a tricky technique (which I'm pretty sure is covered here). With a high quality, new, non-stick pan you might also be able to get away with a truly negligible amount of oil by dampening a paper towel with vegetable oil and wiping that on the surface. Mimicking the so-called-fat-free-sprays by using a paper towel dampened with vegetable oil might be a much better choice for you.