Vitamin B-1 + minor elements or S.T.E.M for iron deficiency?

My vegetative plants, or more specifically, one plant, is showing the beginnings of a deficiency which is either iron or sulfur per a leaf chart I downloaded some years ago. I do not have a bottle of SuperThrive on hand, but had two other items that supply iron. One was Western State's brand Vitamin B-1 with iron (0.125%), manganese (0.125%), zinc (0.125%), all derived from sulfates with EDTA added as the chelating agent. The other source was Peter's S.T.E.M. powder. My fertilizer formulas (nutes) already include S.T.E.M. (0.2 oz/100 gallons), but it can be increased to 0.3 oz/100 gallons and still be a label-suggested amount.

Which product would be more likely to successfully treat my plant's iron or sulfate deficiency? I'm leaning toward increasing S.T.E.M. Another tactic: Mulder's chart indicates synergism between K and iron, perhaps I should increase K, use 3-1-2 instead of 3-1-1?

Any thoughts?

Problem solved?

Thanks. Yes. I changed the procedure of how I weigh my nute's ingredients. When I started adjusting EC, I was not thinking correctly about S.T.E.M., I was adding it before the dilution, instead of afterwards. I'd put up a pic, but haven't downloaded it yet to laptop from camera.