Hello I have four white widow plants growing in soil under a 250W MH light 12in. above plants once a week I fertilize with 20-30-20. They are just over a month old now and one of the plants leaves are starting to get brown spots then brown and yellow around the edges and eventually die and fall off and the other plant seem to be starting to follow suit. What am I doing wrong this is my second grow did the same as last time and had no problems. I water them every two or three days when the soil is dry.
I would highly recommend checking out the sticky at the top of this sub-forum about sick plants. If your leaves have brown spots and are curling up it is most likely a calcium or magnesium deficiency. Also if they are experiencing necrosis ( symptoms are crunchy, yellow, dead leaf tips that soon work there way into the interior of the leaves) then that is another symptom. I would highly recommend checking the pH in your soil, as you might be experiencing nutrient lock out ( magnesium and calcium are locked out in soil under 6.4 and absorbed best in 6.5-6.9), but if the pH is fine I would highly pick up a product from Botanicare called Cal-Mag Plus ( Calcium-Magnesium + Chelated Iron). It is great for supplying those macro nutrients you might be missing out on in an all purpose nutrient. Hope this helps man!