More details need to be known before an answer is given.
From the questions and based on my experience, I can ASSUME that the original WPS was used for GTAW root and the rest by SMAW. Because there might be a reasonable joint thickness to necessitate the use of SMAW process besides GTAW for the rest passes, preheat is a concern for non-austenitic carbon or low alloy steels. And let me ASSUME more...the filler metals (for both GTAW and SMAW) match the base metal an it's not a dissimilar metal weld (DMW) we are dealing with....
It should be noted that for similar cases often the WPSs written by experienced engineers specify lower preheat temperature for GTAW root because of the non-flux/low hydrogen GTAW process and less joint restraint at the beginning. But for the rest SMAW passes higher preheat temperature is to be specified. Now we've found cracks by MT/PT and an 1" in depth groove after crack removal, are we going to fill this groove with GTAW following the original WPS with lower preheat temperature?
An approved repair procedure including qualified procedure(s) is always better than assumptions by the ones other than the responsible welding engineer.