Hey everyone 
I’ve been having this problem for a few weeks now, and posted here thinking it was a potassium problem with the rusty spots and all, but now I’m not so sure. I gave two healthy dressings of wood ashes in the first 2 weeks then when that didn’t seem to help I switched to an organic bloom/fruit type fertilizer to make sure the potassium was actually available to the plant. (9-16-16). 2 weeks of that now and still these rusty spots keep coming back. Always on the oldest fan leaves never on new growth and eventually the leaf will go yellow/brown and then die. I have active worms in the soil and with the year we’ve been having almost exclusively rain watered with a bit of tap here and there. Any help or thoughts would be greatly appreciated 
. Thanks
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I’m saying it’s a cal-mag issue, leaning more towards magnesium @fangorn. From your description it’s definitely a mobile deficiency.
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Thanks. I went with that idea last night and put in some Epsom salts. I like that progressive deficiency chart there. Very helpful 
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