Question
Hi, I bought a pot of purple/ pink phalaepnosis a month ago and have been enjoying the blooms very much.

Just 4 days ago, I left home on a short trip and made sure to water my orchids before hand. Upon my return, all my orchids including the newly blossomed ones started to close up as of those flowers which bloomed earlier.

Why is this happening?

I have since watered my plant with a weak dose of fertilizer hoping that this might help.

Answer
Min, it is difficult to know the condition of the potting mix when you purchased the plant.  Since your plant has finished flowering this would be a good time to repot your plant in fresh orchid potting mix.  To know whether root rot might be the reason for the flowering problem, you will need to unpot the plant and rinse off the roots.  Any roots that have collapsed, or are stringy, are suffering from rot and need to be removed before repotting. Feeding a plant with a compromised root system is not likely to achieve anything. When repotting, use a plastic pot with lots of drainage holes in the bottom. Use a commercial grade of orchid potting mix that contains fir bark.  Soak it well before repotting your plant with it.  Wait for at least a week before watering after repotting. Do not let your pot stand in the water.

If the roots seem like they're in good condition, then it may be that you lost the flowers from a temperature drop, or a potting mix that has dried out. In any event, repotting will give your plant a head start in setting out on a new growth cycle with new roots and leaves.  In the interim, it is possible that your plant could grow new buds.