First and very budget grow -Super Lemon

Early in week two i transplanted both to their final 30L containers with the same ratio of Soil, Perlite and Coco, but shortly after both plants got some rusted spots all over the lower leaves, and afterwards it even did some bending. I Figured this could be a Ca/Mg/Fe deficiency, due to me believing "nah, my tap water ph must be fine". After buying a soil and a water ph meter, i discovered soil ph was all the way down to 3.5, and my water was aroud 5.5, and after correcting the ph the plants got back to growing, yet, the damage to the early leaves is done and i trimmed a few of them.