800 ppm is more than enough to keep a plant that small green. You have a lockout or some other possible PH related issue. As already mentioned 600ppm tap is very high. I wouldnt use tap to grow if it was over about 350. I'd get a filtration system too, but not RO cuz then you're just gonna have to add cal/mag as well.
"wataring:4x1h - 30min. in and 30min out water" What is 4x1h? 30 min on 30 min off leads me to believe you're watering every 4 hours? I would increase the freq to more like 15 min per hour, or 15 min every two hours.