At 38 days in, it’s common to start seeing some nutrient deficiencies, especially with autoflowers as they move quickly through their growth stages. Based on your description, it’s possible that the issue could be phosphorus-related, but here are a few signs and other nutrient deficiencies to consider:
- Phosphorus Deficiency: Look for dark, purplish or reddish patches on the leaves, particularly lower down on the plant. The edges of leaves may look burned or browned. Phosphorus deficiencies can cause slower growth and weaker stems.
- Nitrogen Deficiency: If the leaves are yellowing from the bottom up, it could be a nitrogen deficiency. Autoflowers often use a lot of nitrogen in the vegetative stage, so yellowing can mean it’s time for a nitrogen boost.
- Potassium Deficiency: If you’re noticing brown or burnt-looking tips and edges on the leaves, it could be potassium. Leaves might also look dry or brittle.
- Calcium Deficiency: Calcium issues often look like brown spots or holes appearing on leaves, and newer growth may look distorted.
What to Do:If you’re already using a balanced nutrient blend, try slightly increasing the phosphorus, especially if you’re in a bloom stage. Make sure your pH is in the correct range (around 6.0–7.0 in soil) because nutrient lockout can happen if pH is too far off, even if nutrients are present.