Adding a teaspoon of Epsom salt to a gallon of water
need more info how old are they 12/12?
pics your run off ph
would you like me to copy a support ticket for your?
Your problem is most likely nitrogen. Nitrogen is a mobile nutrient, which means it can move throughout the plant as needed. Cannabis needs nitrogen to keep leaves green and make energy from light. All new leaves get plenty of nitrogen to make them green and help with photosynthesis. The leaves that get the most light are the newest, youngest leaves, so the plant “wants” to give those leaves priority for getting light.
But as Donald said, more info is needed.
Anyway here is the Support Ticket…“.pic’s would be very helpful”
COPY/PASTE: This “Support Ticket” into your forum post.
Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA
Strain; Type, Bag seed, or NA
Soil in pots, Hydroponic, or Coco?
System type?
PH of runoff or solution in reservoir?
What is strength of nutrient mix? EC, or TDS
Indoor or Outdoor
Light system, size?
Temps; Day, Night
Humidity; Day, Night
Ventilation system; Yes, No, Size
AC, Humidifier, De-humidifier,
Co2; Yes, No
Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the point questions and facts will help us help you 
We had a previous Support Ticket posted, but lost it during the “database issuer”
Will