im going to get some better pics and i know i should ph test the soil before adding a nutrient like magnesium to tray and fix it but i have a ph soil test tube kit from a garden centre which is cheap and last time i tried the same one it didnt work? ive got some epsom salts, fish, blood and bone, dried blood and super phosphate ready to add in but i have never added these to my plants yet. The only nutrient feed ive givin them is bio bizz biogrow 0.5 ml the 1st week, 1 ml the 2nd, 1.5 the 3rd and planning on adding 2ml for the 4th which is due today. So am i rightin thinking it wont be a nitrogen deficieny as this is provided for but may be magnesium as its not included?