Could be environmental... could be a little too much of various nutes that can cause similar symtpom. 800ppm isn't especialy high, but is a bit high and autoflowers are notoriously picky eaters.
i don't see other symptoms, so double check pH of runoff and see if it is drifting. Too much heat or light can make a leaf "taco" too. eliminate possibilities of environment and pH before fiddling with nutes.
i have a table of nute ppms each week in my diart. i have hard water so i have to use somethign clsoer to ~650ppm, but the npk values are good. N/P/K ppm of 120s/50s/190-200ish, respectively... within 5-10% is probably good enough.