I am also growing Moringa from seed (in my case, in a mediterranean climate). Are you growing them in pots right now? Could it be nitrogen deficiency? Two strategies I've tried when having issues was a) dilute
urine b) worm castings on surface of soil (covered with a little
straw to stop from drying out) c) alpaca manure tea (some alpaca manure in
water, stirred occasionally for 24 hours or so then applied). I have almost killed one or two moringa because they got waterlogged, but then they recovered and grew a new stem once I'd let them recover.
Spots sounds like disease is a possibility, though? Let me know what you find out. Good luck.