When you made the switch did you compensate your torch height? The shielded consumables have to be run 0.030" lower because the IHS system references from the shield cap but the actual nozzle is now recessed. So if you originally had your cut height around 0.060" and didn’t change it you’re now really cutting at 0.090" which is way too high.
From my experience if you have all that setup properly and everything else is functioning well you should not need to change you feedrates at all. The shielded consumables also seem to require a bit more air flow volume but work well at the same pressure as unshielded.