Debbie, too much light over time can eventually cause yellowing--it all depends how close to your bulbs you're keeping the plant. If the spots aren't burn, they're going to be some kind of infection. Since you can't use commercial sprays right now, wipe the entire plant down--tops and bottoms of the leaves--with listerine or hydrogen peroxide. Then, make a paste out of cinnamon powder and a little peroxide or alcohol, and rub that into the spotted areas on both leaf surfaces. If the spots spread, you're going to have to cut them away.