Hi Eveth,
Your plant looks quite healthy to me. I suspect it is probably just the heat we've had over the past week or so here in Melbourne that will have contributed to the flowers finishing a bit early. If it was in full bloom when you got it, though, there's no way to tell how long the flowers have been open for.
Also, my understanding is that Phalaenopsis can rebloom if you don't cut the flower spikes. I don't grow them and so can't comment on that point, but there is a good thread on growing this genus of Orchids right here in the Orchid forum:
The thread "๐ฃ Starting out with Phals/Supermarket Orchids ๐ โ๏ธ" in
Orchids forum
