I have had my planted tank set up for about 7 weeks now and I am pretty happy with it. However there are 1 or 2 species of crypts and 1 species of anubias that have light green leaves with dark green veins. They are growing and reproducing, just not at the same pace all the other plants are including about 3 other species of crypts. I heard that this might indicate an Mg deficiency, correct? If not what might it be then?