Appendix Carriers, how do you prevent your shirt from getting white spots?

I know it's not the shirt quality, since it happens from my shirts from H&M to Express and Banana Republic. Is there any way of preventing my shirts from getting spotty and white marked?Any help would be appreciated. Thanks!*edit pics: http://ift.tt/2ghVNXV via /r/CCW http://ift.tt/2h0uU9k