I would also ask, did you have the lab scan these or did you do it yourself? It looks like they are slightly "lab corrected" as in rather than give you lab scans as they were, they were brightened up a bit from the original exposure which would account for the increased grain look. Also standard lab scans are often of poor quality. Third, the first image looks like someone hand processed them as I see a bit of bromide drag in the background, not at all terrible from what I've seen but not great either, I agree try over exposing by a stop or ask for push process for one stop, I've read that Portra handles that sort of thing better than any other film ever, so as long as you dial it in properly it should fine.