From what i see 1100 is to high! Do a flush and start back at 1/2 strength till you see improvmentthe nutes were around 1100 ppms and water for 15 min 3x a day.....
That is not over watering! RoflPossible overwatering try cutting back on your water!!!
Wrong. Sorry, but just wrong.leaves curling under like that is a clear sign of phosphorus deficiency.
Maybe not such a daft suggestion. He is using 4 inch rockwool cubes in hydroton. How often does he flood and for how long? how deep is the flood? Are roots established?Possible overwatering try cutting back on your water!!!