Fading irons but not woods

Hey guys,

Seeking some insight.  I recently switched irons from Mizuno MX300 regular shafts to Ping I20 stiff shafts.  My 6-iron in MX300 went about 170.  End of last year, I tended to hook a lot of my iron shots so went to fit myself on a launch monitor and it seemed like I needed a stiff shaft.  So that's how I ended up where I am.

Recently, played about 8 rounds or so (all with the new I20s) and I'm crushing my driver and 3-wood, which is really nice!  But no matter what I do, it seems like my irons are all fading/push fading.  Do you think it's the shaft?  The less offset of the pings?  Ultimately, could it be my swing?  But I love how I'm hitting my woods right now....

1) the MX300 could have more offset, though i doubt, being Mizuno versus Ping

2) It could be the golf shafts, maybe the stiff shafts you have arn't stiff. There is no standard to what a flex of a shaft is. For example Dynamic Gold S300 is less stiff than a KBS tour Stiff. They both say stiff flex, but there both at different levels. So you could have switched to a stiff shaft, but actually went less stiff. Especially if your using proprietary shaft from ping, and not aftermarket or upgraded golf shafts. Its nearly impossible to tell the stiffness with out getting them frequency checked. My taylormade burner irons say stiff, the are regular flex when my pro checked them out.

3) Your swing could have changed, its natural for driver swings to be a bit more flatter.

4) The lie could be off, which could cause a fade.

thanks saevel,

2) the pings are actually CFS stiff and the mizunos were TT Dynalite regular

4) I was thinking about the lie issue since I see a lot of hits off the toe.  But that tended to be from the 7-iron and longer irons.  Not really sure what toe hits mean in terms of ball flight, etc

is it common for someone shorter at 5'7" to have clubs bent upright?

I am about a hair under 5'8" and play G25 yellow dot so they are upright 1.5*. I know mine are right I went to 4 fitters before I finally settled on one guy but all stated up right, it  got rid of the inconsistency with catching the toe and hitting the right.

As for shafts I play reg CFS and love then but they are a good fit for me.