I have a 5-yr old or more de Buyer 12" mineral b fry pan I use for everything from omelets to clams and linguine. Today I noticed something that looks like hairline cracks on the inside surface. Seven or eight about 2" - 3" long. All oriented along same general axis. My fingernail catches on their raised edge but I don't see anything on the bottom or any leakage. Otherwise all is great. Any ideas?