naw the water wont act as a magnifying glass except under truely intense light, also if the humidity is high the droplet will take longer to evaperate and damage over time can occur.
never foliar feed at full str, as it will burn if your getting enough nutes from the roots.
never foliar feed after week 2-3 of flowering for indica, 4-5 for sativa. (i dont like smoking dried fert residue)