Text. Hit this link. It'll take you directly to the plant problem FAQ section of this forum. Pics and Info all there.

Magnesium
Chlorophyll has the same structure as Hemoglobin, except that it has a magnesium atom in place of the Iron atom. Chlorophyll is how plants make sugars to feed the process of building ATP through the Krebs cycle.

Magnesium deficiency

A magnesium deficient plant is identified by intervenial chlorosis, necrosis, and eventually a lockout of plant nutrients. The problems starts at the bottom of the plants and works it?s way up.

Magnesium deficiency

These images depict different stages and signs of a magnesium deficiency. The first picture is a Mg deficient plant in flower, and the second two are of the leaves to show what I mean by Intervenial Chlorosis.

Magnesium deficiency

Treating with an Epsom salts mix will clear this right up.