Blackening of leaves in your plants can be caused by various factors. While nutrient excess is a possibility, there are other potential causes as well. Here are a few factors to consider and steps you can take to address the issue:
1. Nutrient Imbalance: Excess or imbalanced nutrients can lead to leaf discoloration. In your case, as you suspect nutrient excess, it's worth examining the nutrient levels in your hydroponic system. Ensure you are following the recommended dosage for the GH 3-part system and calmag supplement. You may want to reduce the nutrient concentration and monitor the plant's response.
2. pH Fluctuations: Even though your pH range appears to be within the acceptable range, fluctuations can still impact nutrient uptake. Monitor the pH levels closely and try to maintain a stable pH around 5.8. Frequent pH fluctuations can cause nutrient deficiencies or excesses.
3. Water Quality: Since you are using reverse osmosis (RO) water, it is essential to check if any impurities are present. Sometimes, using pure RO water without any added minerals can lead to nutrient imbalances. Consider using a nutrient solution specifically designed for hydroponic systems or add a small amount of mineral supplements to your RO water.
4. Light Intensity and Heat Stress: Excessive light intensity or heat stress can cause leaf discoloration. Ensure that your plants are not exposed to intense light or excessive heat. Maintain appropriate temperature and light levels for your plants during the flowering phase.
5. Pest or Disease Issues: Examine your plants closely for any signs of pests or diseases. Certain pests, such as spider mites or aphids, can cause leaves to blacken. Additionally, diseases like powdery mildew or fungal infections can also lead to discoloration. If you observe any pests or suspect disease, take appropriate measures to control and treat them.
6. Genetics: Leaf discoloration can also be a result of the plant's genetics. Some strains are more prone to leaf blackening or purpling, particularly during the flowering stage. If all other factors seem to be in order and the plants are otherwise healthy, it might be a genetic characteristic of your particular strain.
It's crucial to closely observe your plants, make adjustments based on their response, and take necessary corrective actions. If the issue persists or worsens, it may be helpful to consult with experienced local growers or a horticulturist who can provide tailored advice for your specific setup and growing conditions.
i'm growing on hydro, using GH 3-part system&calmag supplement w/ ro water. Ph is around 5,9-6. thanks
