As simple as that what do you think is cause whats in the pictures? Overall its very healthy but this has happened over the last few weeks. I killed a caterpillar on it but that was the only thing i have found and have seen nothing since.
What Strain is it?
Is it Indica, Sativa or Hybrid? What percentages?
How Many Plants?
Is it in Vegetative or Flowering Stage?
If in Vegetative Stage... How Long?
If in Flowering Stage... How Long?
Indoor or Outdoor?
Soil or Hydro?
If Hydro, Reservoir size?
If Hydro, Reservoir Temperature?
If Hydro, what type of Medium?
If Hydro, what type of Setup?
If Soil... What is in your Mix?
If Soil... What Size Pot?
Size (Wattage) of Light? How Many?
Is it Air Cooled?
Temperature of Room/Cabinet?
RH of Room/Cabinet?
PH of Medium or Reservoir?
How Often are you Watering?
Type and Strength of Fertilizers used?
Size or Square Footage of Room?
This information is necessary for accurate support to be given.
Looks to me like phosphorus deficiency, but that could be due to lockout caused by pH problem or other nutrient problems.
If you are feeding regularly with ferts containing enough phosphorus then check pH is between 6.0 and 6.9. Also look into calcium/magnesium problems. Hopefully someone more experienced can help with that. I can never keep nutrient level interactions straight.
For what it's worth, I've had same problem ongoing for months. I played with nutes and pH with mixed results. Finally I switched to new soil that seems to have solved problem (for new plants, old ones still suffering.)
Follow up: I was looking at brown patches earlier. Now noticing other leaves with yellow edges and brown tips. Possible to have more than one defieciency.
The brownish spots between the leaf veins looks like Phosphorus deficiency. Either calcium or magnesium (I think calcium?) looks similar, but is usually smaller dots and more widespread. The brown leaf tips may be nute burn. What ratio fertilizer are you using?
This looks like a severe calcium deficiency. It is probably caused by a ph issue. Your new growth is twisting and curling. This is because calcium is immobile (semi immobile) and cannot be borrowed from leaves that have already stored it. Calcium leads quickly to magnesium, which is what your brown edges look like. If you have a ph issue, you are likely dealing with multiple deficiencies. What is your soil, and what are you feeding. Also, your watering schedule. Believe it or not, the cascade of deficiencies can be caused by over watering.