White lines on shell (incubator, day 8)?

I have six pekin eggs in an incubator. I candled last night and noticed what looked like small cracks on the shell of one of them. I moved it to the side so I can examine it closer in the daylight. This morning, I see that is visible in the sunlight. It doesn't look like it's cracked, but it's definitely there. Should I toss this one? I can try to get a picture the next time I turn them.

This is my first time ever attempting to incubate eggs, so I have no experience and am learning as I go.