I've got the same problem with two indoor plants. None of the others are having any issues but the two started out looking like yours and are now much worse. The spots continued to worsen rapidly. I flushed this morning so hopefully it helps. I'm very curious to see if anyone knows what is wrong with yours.
jcathunter Reviewed by jcathunter on . Leaf Spots and tips burning, odd color in veins Please help take note the issues are on 2 other plants as well which do to people around i cant get any more shots. Look at the sun leaves. ph is around 6 to 7 outside in ground soil last watering was straight water temp @ night droping to 45f - 55f and days @ 70f - 76f day time they get about 6 hours direct light and the rest is a light shade. Rating: 5