I just had the whole lock out on just 1 plant out of many in same mix. Only me. I ran some AACT with RO water and seen instant results! Followed up with an SST with RO water and back in service. Pics would be great of course. If it's a deficiency, than I'd top dress and CT. +1 Spicy!It sounds to me like you need a healthy dose of the organic fix-all; actively aerated compost tea!