DD due to go to NY in a couple of weeks. I noticed today there is a weird mark just above her signature. It’s not pen and signature isn’t smudged. I can’t work out what it is, probably been there all the time, passport is 4 years old and she’s used it regularly with no issues. I’ve googled and general opinion is as long as the photo page is in tact and there are no signs of damage or tampering then no worries, especially on the signature page, but being a peri M lady I am beside myself. Any thoughts?