I doubt its a lack of Nitrogen. we use diluted 5-1-1 fish emulsion regularly. the foliage that ISN'T effected is stunning. nice and green, thick, and lots of it! we just got our first scapes showing last week
im assuming the damage you speak of, in order for the fungus to get in is caused by either slugs or possibly cutworms...? which are in abundance this year due to our record setting warm winter a few months ago...
thanks for the input!