Looks like possible overfert, more like too much P though. If you suspect it, just cut back or try flushing with lots of water. If they perk up in a day, you'll know that was it.
Hey CoCo, I really don't think they look like over dose...
It really looks more like over watering to me.
Maybe even beginning of lock out.
I don't recommend flushing until the soil is dried out, as it'll only compound the problem.