[h=1]Manganese Deficiency[/h]
Problem: Leaves may become yellow in between the veins, with mottled brown spots on the affected leaves. These brown dead patches may spread and eventually kill the leaf. Leaves may also shred and fall apart.
Overall growth of the marijuana plant may be stunted.
Solution: Manganese deficiencies are often caused by a pH that is too high, or if the plant is getting too much iron.
If you have a manganese deficiency in soil, try to correct pH to 6.0 - 6.5l. In hydro, correct pH to 5.5 - 6.0. You are looking to avoid higher pH ranges, as this is where manganese deficiencies are most likely to occur.
Flush your system with clean, pH'd water that contains about half the correct amount of nutrients needed by the plant. Watch to make sure that the problem starts to clear up within a couple of days.