Unless you have some other factor that requires impact testing etc at play, refer to QW-256 which under electrical characteristics where it list the tungsten as a non essential variable, which leads you to 409.12 which states "QW-409.12 A change in type or size of tungsten electrode" the change would not require requalification of the WPS unless some other mitigating factor invoked the qw-409.12 as an essential/suplementary essential variable.

In short I dont' see the problem if it's on face value, no specification, or impact testing required.

Regards,
Gerald