It was nutrient deficiency! I had 2 plants in one pot so it depleted the soil nutrients in half the time due to the two plants. Put them into fresh soil and slightly topped up the nutrients and they’re grand now
Did the new soil have too many nutrients in it already. With fresh transplant and issues from prior question. Not looking really good. Test run off ph and provide light nutrition. Good luck and happy growing. Hope they make it.
Most likely would be toxicity from feeding nutrients (no nutrients required for at least 8 days!) or from damping off. This happens when your medium gets too wet. The roots suffocate and die.