Could be from your foliage getting wet during daytime hours and then the droplets burning off. Also looks like possible thrip damage, so take a close look for those, especially under leaves. Last this is to make sure she has calmag and your runoff isn't too acidic. Make sure these things are in order and she will be good.
I'll also note that it could be a mold starting. If it looks like powdery mildew, do a vinegar or h2o2 mix (check online for mix amounts).