Thank you for the reply.

I usually watered them when I "felt" they were dry. I heard the rule is
to water them once a week, but I was afraid they might die before then,
so I watered them. I suppose they would have done fine even without
water for a full week.

The Oncidium initally came from the grower, so the medium was obviously
fine. They were grown in Hawaii with plenty of humidity. When they came
to Austin, since it's so dry and hot where I left them (in a shade
house), I used a sprinkler and watered them every day. I took them out
of their pot and placed them in coconut husk made baskets.

I saw a dendrobium in Ft. Lauderdale in July that was out open tied to a
tree (not in the shade) at a hotel. The management told me it had been
there for over a year and bloomed again there. I imagine the Florida sun
would have been too hot for that plant, but it managed to survive that.
My question is, without a potting medium, would an oncidium (and zygo
for that matter) survive a week without water? I noticed some roots that
were in the air got killed (had brown tips) after I watered them. I was
using tap water. Would that be the reason the roots died? Or, could it
be the fertilizer that killed them? I have started using distill water,
but haven't seen the results of it yet.

I also have phals, paths, and phrags; but they are a lot easier to take
care of. The Miltonia has new roots coming out. I am walking on thin ice
not knowing what I did right and am just trying to keep the roots growing.

Ray wrote:

Sounds like you're killing the plants before they have a chance to mature
fully. Old pseudobulbs are intended to stay around long after the leaves
that grow on them are gone, acting as food and water storage for the colony
of plants, and as they're still green, will add to the photosynthesis as
well.

In an oncidium, those old bulbs can hang around for years before they are
sucked dry, turn brown and papery. Zygos, in my experience, don't hang onto
the bulbs quite as long, but it's certainly not the direct sequence you
suggest.

If you're drowning your plants to death as you state, either you're
overwatering or using a growing medium poorly suited for your growing
conditions and plants. Can you provide more detail about the growing medium
you're using, how often you water, or other info that might help us be
better guides?