Tombstones?!? :shock:
Jeez, there's nothing remotely resembling tombstoning, don't get the poor guy scared!
Throw out all the strips with artifact, they're useless. The clear ones don't show anything to worry about, not even a BBB, don't even give it a second thought. Like AZCEP said, "Unless you have some kind of bizarre family history of heart problems, I'd let this go. If it concerns you see your doctor."
The problem when you get to play with a toy like that, you look for something to be wrong. Unless you have a reason to hook up (symptomatic), don't bother, you're far too young to worry about stuff like that! Heck I'm over 40 and don't worry it. :wink: