Posted: 04/12/2016 at 15:15
I don't know much about growing lemons, but I agree with Lb - it does look like chlorosis.
Usually a dose of MgSO4 (epsom salts) corrects the deficiency, if it's magnesium. 1 T-spoon in a gallon of water.
There may be other causes such as a lack of iron.
I believe there are 2 different feeds for citrus - a winter fertilizer and a summer fertilizer.
Are you using those?
Sorry if I'm preaching to the converted. The fruits look great