Brown specs

Are the brown spots suppose to stop spreading rite a way when sprayed with epsonsalt been sraying ever morning for 5 day look like it reachd tha tops started from tha middle then went up

what is that confused its a strawbwrryice (indica) have ph at 6.1 and next day 5.5 tha ppm cant go past 400 or it will show stress or get those brown spots its in a dwc and roots look good ff nutes temps no higher then 78 at night 65 humudtiy 50 between 45 2 weeks flowering useib tiger bloom&big bloom any advise pls new to this