Just like all living things, your plants need specific nutrients not just to grow but to thrive. This is something you need to pay very close attention to. Here are some basics to look out for:
Nitrogen deficiencies have a distinct pattern of yellowing. Yellowing starts as light spots on the older leaves until they wilt and die off, leaving the top part of the plant green. In severe cases, the entire plant will turn yellow. Nitrogen is used for the production of chlorophyll and amino acids, don’t run out until you are ready to flush your plants.
Phosphorous deficiencies have a distinct pattern of Purpling. Starting with purple appearing on the branches, then stems of leaves and then the veins of the leaf all turn purple. In severe cases, older leaves will turn completely purple continuing up the plant until even new growth is deprived. Bud size will be considerably smaller and underdeveloped, as will the root mass.
Potassium deficiencies are identified by dead, brown spots forming on the lower leaves. Leaves may also yellow and die. Do not get this confused by a nutrient burn. In severe cases, the plant stems and branches will become weak and fragile.
Calcium deficiencies will cause the medium to become acidic and lower your PH. A shortage of Calcium will appear as both Magnesium and Iron deficiencies. You may also check harvested plants for hollow stems as a sign of inadequate Calcium.
Sulfur deficiencies are easily identified by complete yellowing of all new growth.
Magnesium deficiencies are common and easy to spot. Older leaves will first turn yellow then it will spread throughout the plant. Left untreated, leaves will become crisp and dry when touched. This is different from a Nitrogen deficiency because the veins will remain green and dead leaves will be dry, not moist.
Manganese deficiencies will also turn the space in between veins yellow but on the newer growth. This will progress to brown spots resulting in dead spots on leaves. Plant growth will be stunted and if left untreated the entire plant will die.
Iron is an important component for the transportation of electrons for photosynthesis. A deficiency is identified by new shoots turning a pale yellow, while the veins remain dark green. This kind of mimics the magnesium deficiency, but a pale yellow. This deficiency starts with the lower and middle leaves and will progress to brown spots. In severe cases, new growth will lose the ability to produce chlorophyll, turn a pale yellow and completely stop growing.
EC/PPM too high
Eutrophication happens even to the best of us. Be on the watch for the first sign and prevent it from happening the next time. This is distinctly recognizable by browning of the tips of leaves. This can be the outer points or the outer ridges. Once you see a nutrient burn, growth on this part of the plant has stopped. In the vegetation stage there is time for new growth to emerge; in the flowering stage it can seriously stunt the growth of flowers.