Kamryn from California asks, "What's going on with my leaves? They were green before they bloomed, but now a bunch of the leaves are turning yellow!" If the environment your plants is optimal- meaning the temperature, airflow, and humidity are where they should be for your plant- chances are you're experiencing some sort of nutrient deficiency. Depending on where the yellowing's occurring, you could be dealing with either an iron, nitrogen, or magnesium problem. While these deficiencies can be found in any garden, growers who use RO water usually have these deficiencies more often because things like iron and magnesium are found in regular tap water, and taken out when processed. The absence of them will be seen in your plants if you don't compensate for it, so always make sure your pH and PPM levels are where they should be. Identifying the Deficiency and Correcting It To identify which deficiency you're dealing with you'll want to see where the yellowing's occurring. Iron: When new growth and your upper leaves yellow chances are you're dealing with an iron deficiency. Magnesium: When older, lower leaves start to yellow around their edges you're likely working with a magnesium problem. To fix these issues, flush your plants and get them ready for a new round of feeding. When you add nutrients to your solution, add a Cal-Mag nutrient into the mix to fill in the gaps your old regimen was leaving out. Nitrogen: When lower leaves yellow completely it's usually caused by a nitrogen deficiency. Usually, when a plant's starving for nitrogen it's because the nutrition it receives doesn't have enough in it for the plant to grow properly. It's not very common with hydro plants but it's possible, and soil growers know all too well the problems of nutrient-deficient soil (especially when it comes to nitrogen problems). If you feel your plant's not getting enough nitrogen, upgrade your nutrients one with a higher nitrogen rating in their N-P-K reading.