Spots on leaves

possibly calcium deficiency, but if these are shielded, older leaves, it could be nothing. Calcium will generally show up in upper portion of plant, first. Old leaves that don't get as much light are not as well maintained by the plant. Don't remove. they still perform other functions, like transpiration. CO2 is important. knowing how much Ca you already provide on a consistent basis would help too. Definitely not an infection. If you choose to up your dose of whatever provides calcium, don't go overboard. Ca++ is quick to lockout others. Plus, if you see coinciding interveinal chlorosis, it's more likely a Mg-deficiency. In my experience i see the interveinal chlorosis before the spots with Mg-deficiency, so i'm still leaning Ca.