Simon,
We've had classic Central Florida weather, except its been hotter than normal, though nothing like some pf you guys in Cali have had. I've had a bunch of days at 99, a couple at 100 and even hit 102 on Saturday here. I'm in a bit of a micro climate and seem to be about 2-4 degrees warmer in the summer than the surrounding area - which generally means:
08am - 80 and sunny
09am - 90 and sunny
10am - 03pm - 95+ and mostly sunny
03pm - 06pm - 95+ until the storms hit then mid '80s
06pm - 09pm - gradually back up to 90 then down to uppper 70's or low 80's at night
The main reason for the thought it wasn't sunburn was those plants have had full sun since right after they sprouted. I hardened them on our porch for a week, then did 2 weeks in partial sun, then from January - June when they were planted in the ground they had full on sun every day as we really didn't have much in terms of rain then - maybe 1 day, and they were doing well in the pots, and since the pots were black they were baking in them so much that in May I had to water every day. The ground, i thought, would be better for them and they took the transplant well, just that the worst one started yellowing about 14 days ago and the other 2 started yellowing about 10 days ago.