Croak'- drop us some fresh pics please,.. critical for diagnosis! ..hows that earlier plant looking? I'm leaning toward Zn defc. too,... Fe and S usually yellow out from the center "palm' out to the tips, on new growth,... Zn is an oddy,... Fe and S are immobile (meaning that plant can't yank them from other tissues once established, and move it to high demand areas), so symptoms typically show on newest growth first,... Zn is mobile, but still shows at the very top anyway,...:dunno:... in any case, a foliar spray is a great way to go, along with soil dosing,... foliar is the fastest way into the plant, and for immobile nute's, dropping them right where they're needed most really helps speed recovery along!