i don't know about the weather where you were fishing, but it has been kind of warm this past week in the buffalo area. maybe the water temps have crept up a tiny bit. that might explain it, but it might not.
i fished two consecutive days a couple weeks ago. the water was high and off color. first day struggled a bit until the end of the day when a great bite came on. came back the next day to the same conditions and the fish wouldn't leave the swung fly alone. broadside, fast, slow.... it didn't seem to matter. don't know why the fish were so aggressive. haven't seen it since even under similar conditions, but glad to have experienced it.
heck, breaking the mold only gives you more confidence in the swing when conditions may not be perfect.... and confidence is key.
"God, in his great clemency, created the Earth, Louis Armstrong, the Neville Brothers and ReBirth!"