@Maryjane23, Thanks!
I do not know why the plants grew so compact. Mine look quite different than other Orions I saw. I wonder if I should turn my lights into a lower setting. Any suggestions?
Day 10: Added 0.75 g ammonium nitrate and 1.25g of magnesium sulphate/L and irrigated both plants with 1L. The second pair of leaves started to show
Day 12: The second pair of leaves developed.
Day 13: Added 1ml/L BioGrow and 0.5g/L of magnesium sulphate. Today I can see that the third pair of leaves developing.