Problems with nutrients are not always caused by too little or too much fertilizer. Nutrient problems can also be a result of irregular pH, a buildup of salts in the grow media, or excessive heat or humidity in the grow room. When symptoms appear, first consider environmental factors because they are the most common sources of problems.
If a plant symptom appears, first check the pH of the reservoir to ensure it’s in the target range of 5.8-6.3. If your pH is out of range, your plant problem is probably being caused by the irregular pH of your water.
Rule out that your grow media isn’t a source of problems. A mineral buildup in the grow media causes nutrient lockout and irregular pH at the root zone. A mineral build up can happen if excessive fertilizer is applied, or even just as a result of several weeks of slow accumulation from normal fertilization. To prevent build ups don’t over fertilize your plants by keeping the concentration of your feeding solution within a safe range. If using a media with high drainage like hydroton, consider rinsing your grow media with pure water to wash away excess minerals once per week.
Adding yucca extract to water used for rinsing helps remove a toxifying mineral build up better than water alone.
The relative humidity in the grow room should be maintained at 40-70% for the vegetative growth stage and 40-50% for the flowering stage. There should be adequate air circulation, including fresh air. When humidity is too high plants have trouble drawing up nutrients. Excessive humidity can be a source of your plant’s problems.
The temperature in the grow room when lights are on should be 70-85°F (20-30°C) for the vegetative growth phase, and 65-80°F (18-26°C) for the flowering growth stage. Excessive cold or heat can cause plants to struggle with processing nutrients. It’s okay if temperatures cool down a bit when the lights are off.
Irregular environmental factors hinder plants from processing nutrients properly. Always consider the overall state of the garden first, before subtracting or adding more fertilizer.