You may have two problems- the RUST colored spots from one source and the silver trails from the other, or the rust spots could be scarring from the damage of the trails... lol confused?
I think you have pests causing the trails. The spots COULD be k def, or they could be scarring. A bloom fert with more K isn't a terrible idea for next time if that's the case, and I doubt you have lockout keeping up on your other stuff so well. But either way there's the bug problem. A pair of pyrethrin bombs set off 4 days apart will kill ANYTHING bug-like in there. Go! DOOOOO IT!!! Get'em.