I have 3 clones, this one is doing the worst. My setup is a 4x8 tent with the clones in the 4x4 veg section of tent. They are in an Ebb and Flow system with a pump pushing water into single tubes to top feed untill roots are long enough. Medium is clones in rock wool for 2-3 weeks untill multiple roots coming out of the bottom. 3-4 days ago I transfered into 3 gallon bags of expanding clay pebbles. I did wash and ph the pebbles for 3-4 days untill water ran clean and ph was stabilized under 6. Ph and ppm on day 1 pic was around 6.5 and 1000ppm, and then today, day 2, it was at 6 (added ph down after yesterday, also added more today to get closer to 5.6-5.8). Water temp ranges between 63 and 68 degrees depending on the tent temp. Lights are 1000watt LEDs of veg spectrum and running 18hours. Water feeding occurs twice daily, once after lights have been on for an hour and once an hour before lights go off. Watering occurs for 15mins. Temp ranges for 70-80 degrees fahrenheit. If I missed anything let me know. It may be worth noting I lost like a dozen clones to over watering the rock wool. This is my first hydroponic grow and am struggling a bit, so any and all advice is appricated.

Photo 1: 3/4 days after transferring rock wool cube to clay pebbles in cloth bag.

Photo 2: clone next day, side angle to show leaf damage.

Photos 3 and 4: nutrients being used

Also today noticed that my heathier clone is starting to droop, making me think over watering. So I've swapped watering to once a day 6 hours after lights on.