botched night sights installation

[KMB]

I'm hesitant to "name names" in this thread, because I don't want it to turn into a mud slinging fest, I'd really just like your advice on what to do. Okay here's the story:

About 2 months ago I went to a reputable local shop (I've purchased from them several times, always been happy, but this was my first experience with their gunsmith) to have a set of trijicon night sights installed on my glock 19. I brought the sight set with me as the configuration I wanted wasn't available locally (as far as I could tell). The gunsmith did the work while I waited, I was happy with the price quoted and the guy seemed nice enough. When ringing me up he said "keep the receipt, if they need adjusted, bring it in with a used target and I'll adjust it for you". At the time that seemed like a nice offer, but I figured it wouldn't be necessary. The pistol consistently shoots about 1 foot left at about 25 feet, I've had several others try out the pistol to eliminate "user error", they all agree "it's shooting way left". The pistol in question isn't one I use all the time, so it's mostly been "resting" in the safe. A few days ago I took it out to clean it (I have always cleaned it after shooting, and usually clean it 1/mo when I'm not shooting it) and noticed that rust is starting to appear all over the rear sight. These sights were ordered direct from trijicon, less than 4 months ago. I've never had anything like this happen with any other sets of sights in the past. Is it possible the gunsmith some how scratched them up during installation and thats what's causing the rusting? Or are they most likely defective?

So here's what I'd like to know: Should I even bother taking it back to said gunsmith for adjustment? (seeing as how I have very little confidence in the guy at this point) and who should I pin the rusting issue on? (the gunsmith, the factory, or myself) Any thoughts would be greatly appreciated...