Is it the silpat?

This was my first time using a Silpat and I have a feeling this is why my cookies turned out this way.. has anyone else experienced this or have experience using a silpat for baking? I make cookies weekly using parchment paper and never have this issue 🙄 If it’s not the silpat, I’m blaming the butter 🥲 I even put them back in the oven and still the same result.

The second picture is for reference how they typically come out . (my family likes a gooey cookie so they’re always slightly under but never this)