i grow in coco. My ph is always 5.8 or 5.9. Growing in coco should be treated like hydro in some ways... but like soil in other. Soil for the amount of nutes to use... hydro for the ph of your nutrient solution. For a young plant 600ppm seems a bit too much. Try cutting back to 400-500. I'm looking at the back of my nute (floranova) bottle and it suggests values twice as high as I use... because its suggesting for recirculating hydroponic systems. If I check their websight, it gives me much lower amount of nutes to use for what I grow in... and what you grow in... which is a "drain to waste" system. Also, I don't do ppm... i do ml/gallon... so I'm trying to convert everything. It seems like you are not using enough CaMg. I use 5-10 ml/gallon of CaMg. If I'm doing the math correctly... that would be 500-1000 ppm CaMg that you need, not 50-100...?