What is wrong with these leaves?

Flood and drain, hydro, Cookie cuts day 12 veg from rooted clone light feed at 5.9 ph, getting these brown spots and burns, 645 leds 5 feet away, rockwool runoff 6.8 ph and runoff ppm 700

is it nutrient lockout or burn? Seem like all have same symptom

Also seeming to have Algae on most of the rockwool cubes

That is almost certainly Calcium/Magnesium Deficiency. Yellow veins within the leaves almost in line formation. You appear to have a decent amount of nitrogen being fed to the plants. I would attempt adding some CalMag+ and see if it clears up in 48 hours.

Herpes.