I think just the opposite of your actual strategy, autos are light feeders, those brown tips and EC runoff upping makes me think you’re near a nutrient burn. When it happened to me I saw those diffuse discolorations, not proper of any deficiency.
I would flush with just pHed water and check the runoff EC and ppm, maybe there are already salts accumulated or a nutrient lock.
A hungry plant is easier to recover than other with nutrient lock or burn, ease down the ferts and see how she reacts, a pic of the whole plant would also help … 