Zinc rot. It is common on post '81 pennies for the copper plating around the mint mark to break during striking, exposing the zinc core to the elements.
Between the I and the T is a die crack. I think the tail of the T shows a die crack and the cross of the T shows plating bubbles with some zinc rot.
Thank you to all on this thread! On my latest search I came across this, and was going to post on them but I don't think I have to anymore. Thanks So this would just be zinc deterioration?