It's just getting old. Starting to yellow between the veins. It will eventually turn completely yellow and fall off.

If your plant doesn't wilt while the soil is still moist, the necrotic areas on leaf tips and margins is from over-watering and/or a high level of dissolved solids (salts) in the soil solution. The best fix, and the one that makes the most sense, since it will rid you of both issues, is to get your plant into a soil that allows you to water correctly w/o worry that you'll rot roots or your plant will suffer from diminished root function for days on end. There ARE ways you can deal with excess water retention, and now isn't a good time to be repotting, so my suggestion would be to start a conversation centering around dealing with excess water retention for the temporal, with a projected plan for next summer that will get your plant back on track. You can't expect a happy plant if you can't keep the roots happy, and fighting your soil for your plant's vitality surely isn't a good way to improve your proficiency. Al

Plants have their own sense of time that isn't measured by the hour hand on a clock, rather, day length (technically it's the length of the dark period) is what the plant pays attention too. When the day length signals the plant to grow, and other cultural conditions allow it to grow normally, your plant should from that point forward start producing healthy growth. It can't 'repair' the damaged growth, though that will eventually be shed and forgotten as the plant grows. What you're seeing is probably the result of an ongoing shedding process that may well have been instigated by conditions that affected the plant even before you acquired it. Your very best coursed of action is to make a good plan that A) ensures good root health B) takes advantages the plants more robust periods and makes allowances for when the plant would be better off without extra human generated stress C) has you ensuring cultural conditions in the area of light, temperature, and nutrition that subject the plant to the lowest level of stress you can comfortably manage. Fortunately, these things are much easier than they sound, but it's not realistic to expect to see the results of your efforts in a month or two. Choose a course, stick by it, be patient. If the course is a good one, your plant will cooperate. If it's not, it will let you know. Al

I found a topic while digging through posts from Gardenweb past-is this the exact issue you're having? http://forums2.gardenweb.com/discussions/3396928/new-growth-help?n=16