Dutch passion ultimate fem issues

[DoggyPutIn]

Dwc,grow tent 2mx2m,600 HPS watt bulb,day temperature 30-night temperature 23,RO water(30ppm),canna aqua vega +Calmag GHE(Cal-4%,Mag-1%),cannazym,ph up.hello friends!the first time here,I ask for your help!ditch passion ultimate fem 40 days of vegetation ,the last few weeks I have been experiencing problems that I cannot solve,rusty dots appear on the leaves and the lower leaves turn brown,my tap water is 317 ppm but I use reverse osmosis with a mineralizer(29ppm)yesterday I made a new solution of ro water(29ppm)+1ml/l ghe Calmag CaO-4%,MgO-1%(260ppm total)+3.84 canna aqua vega A+B(1320ppm)+ 5 ml ph up (6ph),I use ph up because after adding fertilizers, the solution has a pH of 3.5.after adding ph up, the total ppm is 1270.after 15 hours after I checked the solution -1170 ppm and 5.6 ph,new small rusty dots appeared,I forgot to say the plant is already 7 day 12/12 dear community please help me and forgive me for mistakes English is not my native language and this is my first post in life,sincerely grover from russia)