Sounds to me like you used the wrong surfactant. The ProSedge label calls for only non-ionic surfactant containing no less than 80% active material. Using MSO can injure turf.
Although the Celsius label says MSO is acceptable for use, Iíve seen phyto from that combination, too.
I think the lesson is pretty clear here: donít use MSO unless the label specifically calls for it. If youíre not spraying Drive, you probably donít need MSO.
The discolored spots should recover, but donít fertilize them Ė that will just make it worse. Give them enough water so they wonít dry out and youíll see improvement in a couple of weeks.