I doubt it's low boron as REMO has some in all 3 of it's base nutes. 20 Mule Team borax can be used for a supplement. Sprinkle a tsp on top and work it in a bit then water as usual. Or get some boric acid from the drug store and a tsp in 10gal is lots. Add to the water before adjusting pH as it will act like weak pH Down. It's a very rare deficiency.
Looking at the chart I think my damn kush might need a dash of boron as it keeps dropping yellow leaves but is still bushy as hell.
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