It looks like a combination of zinc and magnesium deficiency. If you are gardening on limestone, the necessary minerals may be bound up by high pH, which can be corrected by adding compost. If you are gardening on sand, add volcanic ash or lava sand to add these minerals, or add small amounts of Epsom salts and zinc sulfate, which works faster but doesn't last as long. In a pot, just use a complete food with micronutrients--they'll show up in the "Guaranteed Analysis". If you are close to the beach, salt spray can cause similar symptoms.