Question
I bought an Amethyst minicatt three weeks ago from a reputable outlet. It
looked fine when it arrived. Three weeks later, one pseudobulb was yellow. I
checked the roots of this small plant ( 4 pseudobulbs) and they were brown
and soft and falling apart. I only watered the plant three or four times. Could I
have caused this much damage so quickly? I let the water drain. The plant
seemed dry when I watered it. It is planted in coconut and white material.

Can I save it now? I read about the man with his grandmother's orchid.

Must I cut off the bad roots?
Is there much hope for such a plant?
Should I expect the person who sold it to me to replace it?

Thanks for all your help!
Nancy

Answer
Nancy, it is unlikely that all of this root rot ocurred in three weeks.  The potting mix was probably not fresh and some root rot must have already been present when you bought it.  I would return it with the receipt.  Most reputable outlets will replace a plant-- no questions asked.  So, try that first.

In the future, immediately repot a newly purchased plant in fresh orchid potting mix unless the potting mix looks fresh.  In the process of repotting, clean all of the old potting mix from the roots, then check the roots. Remove any "mushy roots" that are dead.  Many such outlets simply don't have the time or experienced personnel to check the roots, repot the plants that need it, and otherwise maintain the plants in their inventory.

I would stay away from a potting mix that contains coconut.  Coconut has a reputation for retaining salts that can damage young roots.  To use coconut requires special treatment prior to use and there may be no way to know whether it has received that treatment when in a potting mix someone else has prepared.

Minicatts can be very pretty and space savers but, in my experience, they are difficult to grow.  This isn't just my experience either as I have heard this from commercial orchid growers.