Several factors may cause orchid flowers to wilt. Generally it's due to sudden temperature changes or the presence of ethyl gas (as from ripe fruit or the stove), warns Orchid.com. Pluck the wilted flower and change the plant's temperature conditions or location to protect the other blooms and buds from wilting.
Blooms Are Spent
If your orchid's flowers have all wilted but the plant is otherwise healthy, with thick, green leaves that aren't wrinkled or drooping, don't pluck the wilted flowers--it's time to cut the old flower and wait for it to rebloom. Instead, cut the stem up high, just above a "node" (small bump on the stem), and just below the lowest bloom, advises Beautiful Orchids.
If a bloom wilts quickly (within days), then something in the environment is affecting the plant. You should pluck the wilted flower and change the conditions. If the flower has thrived for the past three to four months, and the plant remains otherwise healthy, the blooms are spent and the stem needs cutting. Depending on the type of orchid, and with some care, it will rebloom once a year, several times a year or continuously, says Orchids.com.