orchid newbie: Psychopsis Kalihi with soft, yellow & black leaf

[groundpounder17]

Hello everyone! I'm new to orchids but I've been doing my research. About 3-4 weeks ago I purchased 2 orchids from orchidweb, a Psychopsis kalihi and a Phal gigantea. The psychopsis was in spike and looked rough on arrival. It had some broken and brittle green leaves, some with many black spots. One of the leaves was soft and yellow at the base fading into a small black region. The leaf has become softer and yesterday during watering the leaf was easily plucked from the plant by accident. The buds are tight but very dry. I repotted in an orchid bark mix upon arrival. I use distilled water and Feed Me orchid fertiler, usually watering about every 4-5 days. My plants are in a south facing window. My concern is that this could spread and kill my plant. The phal gigantea is doing well but the two small base (bottom) leaves are wilting, turning yellow and dying which I understand to be normal aging. The top 3 gigantea leaves appear to be healthy and green although the newest is very pliable. Any advice would be greatly appreciated! Thanks in advance.