So....you didn't heed my warnings about the conductive paint being a horrible idea for iPad mini backlight repair....
This is definitely a short caused by the conductive paint. I see a dozen iPad mini backlight repair "oops" cases a week, and the ones with the conductive paint are the worst.
You need to get a toothbrush and some alcohol and do your best to scrub that stuff out of there. Send it in for a proper fuse replacement, and cross your fingers that the short was only the conductive paint, and not that the conductive paint short caused a heat build up under one of the chips that melted some solder balls to create a permanent short.
And then throw that pen away.
jessa