I'm totally new to orchids, so I need some help. The orchid has been under my care for a few weeks and for the last maybe week I have noticed black spots on some leaves and a few leaves have yellow tips. The orchid once a week for 30min gets a soak of water, when I say soak I mean I put it in a shallow diss of water. The water goes half way up the pot. It's at the top of the 2nd floor stair case and it has a south facing window.
What is causing the black spots and the yellow.