Leaves Turing brown

New leaves turning brown and old ones. I haven’t added any nutrients yet, just cal mag every time I water(distilled water), Also I know my ph is high and needs to be adjust but is this causing the leaf discolor and dying of them?

4 1/2 weeks in growing dos si dos and a unknown.

dos si dos: ppm: 964 Ph: 7.5

unknown: ppm: 1826 Ph:7.1

Temp between 76-81

humidity: 45- 55%

soil, farm fox

Photoperiod plants

Any help we’ll be much appreciated it.