Sunburn is likely. I would just move them to a slightly shadier spot or a spot which gets morning to early afternoon sun and then shade. Were they near a masonry wall? 102 should not be a problem for an acclimatized and hydrated plant.

Are they outdoors?

Jane

I believe they initially were outside and then the OP move them in after noticing the sunburn. If the OP is in a place where it was 102 degrees last week I would be very surprised to find a reason to move them inside versus a less intense location. However, at those temps I would be watering at least daily any container under 5 gallons.

Thanks for the comments. I've mostly moved them in under the lights now, it's been 45-ish at night and still too cool out when I leave for work. I usually put them out for a couple hours when I get home. It's been 75-85 during the days now. The soft/burnt areas seems to have hardened back up mostly, still not much going on for leaves (for any of my plumies), but maybe that's just the time of year.

102 to 45 yikes. High Desert?

Yup. Summers around 100-105 days often, 55-ish at night. Winters maybe 65-70 daytime, easily into the 30s if not 20s at night. Won't be planting in the ground here!