Old thread, but I'll add: Stop using an acerbic acid like Windex on your Glock and especially inside your slide! If you're using a 6# striker spring then it's, also, a good idea to use a 6# trigger spring too. (Better trigger pull!)
Your slide channels should be thoroughly cleaned out with Q-Tips and some sort of CLP solution at between 1,200 and 1,500 round intervals. Just before you finish cleaning run a few dry Q-Tips around everywhere inside the slide.
It ain't your Glock; it's the crappy filthy dirty WWB. The FTF rates you quote are all too typical for this kind of cheap target-quality ammo. If you can get your hands on Blazer Alumium I'd suggest you try some. Fewer FTF's and they feed like slick glass. Glock pistols seem to love alumium cases!