:smoking:-- looks a lot like a lensing burn caused by a lingering droplet of water/nutes under high intensity light,... nute' solutions are not inherently bad on leaves, quite the opposite, foliar feeding is a common practice across the entire plant industry... but it has to be done right, under the proper conditions and with water spreader/wetting agents to prevent beading up, which makes droplets act like a lens, concentrating the light into a damaging intensity,... just mind those occasional droplets!