Definitely a plugin as those are not PSP files.
You can disable one by one and see which one is causing it.
i think bbsfmundub is for making the Kingdom Hearts Birth by sleep final remix into Undub and macrofire is for remapping. files are not that much take space.. less than 1 mb.. if i remember correctly i dont have this plugins back in 2014 and i still got have these pass files.. maybe these pass files are cache.. so memory card will run faster. not sure though..... i've never seen these plugins before.
macrofire is a tool for installing plugins
npdrm free is for playing psx/psp games without the license file being present.
bbsfmundub is for remapping controls and fine tuning them to your liking.
i don't think any of these programs would create the blank files that you got.
do the files take up space or are they empty?