Is there a PEX decompiler?

I lost some PSCs but I still have the PEXs.

Yes, here's one on Nexus that I've used before. It requires use of the command prompt, but input is simple and only requires the PEX file name for most situations:

http://www.nexusmods.com/skyrim/mods/35307

OH thank you!

I was too eager in packaging a new release that I accidentally copied OLD source files (from last year) from Skyrim's "scripts\\source\\" folder over my new local SourceTree repositories - which I hadn't commited for a month.

I only intended to copy the new PEX files.