For the micros, it depends on your situation, and your input water ( always remember that RO or DI removes some of the ions, but not all, and a substantial amount can be left of some of them, even up to phytotoxic levels as boron). But orchids definitely benefit fro micros supplementation, if you know exactly what you are doing.
The symptoms of micros deficiencies in orchids are exceedingly tricky, because some things like zinc will show a general plant chlorosis, and the new leaf still emerges dark green albeit small and narrow, which, for other crops, tells it is NOT zinc. Orchids are slow growing, they are using specific pathways more similar to succulents and some palms, so the 'immobile' elements can in fact move inside the plant.
This said, figures about iron in the potting mix vs. in the leaves are most of the time wrong. iron can be soluble, and easily detected in a water extract of the potting mix/soil in the forest. It can be insoluble in various states, and in some of those states, like iron oxide, the plant's roots still can extract it. In the latter case, a water extract will show no iron at all, or a very tiny amount, but in fact the plants still can extract, and even be poisoned by it. This is true for most ions anyway.
