Plant Deficiency

What nutrient is this lady lacking? The lower portions of the plant are nice with a healthy green color. The upper leaves are lime green and have yellow patches on the blades.

 

I foliar fed the plant with fert with chelated iron on the leaves that were affected. In less than a day later i could see the yellow patches start to mimic the nice green leaves under them. They still have spots but if i keep giving it the iron through the leaves it should fix itself thanks to your advice. Someone told me iron runs slowly through the plants and thats why i foliar fed. I also gave it a diluted fert poured into the soild due to foliar feeding(dont want to nute burn the girl). Its fifty days old and been on 12/12 for ten days. Shes 2' 9'' and her sister also showing pistols just like her but had no problems which she had. The only fert i gave it was when i put it on the 12/12 cycle which is 10-52-10. The soil was brand new so i didnt see adding ferts for the forst month because the soil is enriched with them. Thank you again. Peace!

 

Just some pics. no big deal.