I'm not sure what it is, but I would cut the infected part off and treat with a fungicide (such as Ortho Disease Control) just to be on the safe side.

What is that white or silvery looking stuff on it? Not slug or snail slime is it... Do these yellow spots represent the removal of the surface layer of the leaf?

the white stuff is daconil, and it doesn't appear that the surface layer is removed.... it's just spots similar to leaf spot but not quite the same

This is just a guess, but try fertilizing with magnesium, such as what is found in epsom salts. I had spots similar to that last year on one cultivar and decided it looked like the leaf was not manufacturing chlorophyll. I gave it epsom salts, 1 tsp per gallon of water. havn't seen the problem again.

I have had this and it has not caused any problems. Only looks bad. It appears in late July. The new growth does not have it. I would cut the leaves off that have it and destroy them.

I also have seen overspray from Roundup type products make spots like that.

Mike G