Eyyy, thank you! *u*
Nice catch on that! It's not a bug, it's a feature ;] especially for people who found the first playthrough a bit unmanageable x]!
(and about them not going over 2, its meant to be a 3 upgrade system for each one (because anything higher than that would be too overpowered for a single upgrade xD) )
Thank you for bringing it to my attention tho! (≧▽≦)