| Hi Mark and welcome to the forum.
I don't know of only 1 40 watt bulb will be enough. When I grew under lights I used 2 40 watt bulbs.
You've got plants that need quite different levels of light. The Phal can bloom at the lower end of medium light levels; the Oncidium (Oncidium is the proper name for "Cambria" which isn't actually an orchid name at all), Miltassia, and possibly the Dendrobium needs more, at the higher end of the medium light spectrum; and the Vanda is a high light plant.
I'm afraid a single light level somewhere in the middle of what these plants like might enable them to grow but may not be enough to get them to bloom.
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