I have a phalaenopsis orchid that I bought 3 months ago at the mall. The leaves started turning yellow a week ago and now they're kind of soft, almost like they're rotting. I have it in a plastic pot with moss and I water it roughly every 5 days. What am I doing wrong?
The problem is overwatering combined with the moss that holds too much moisture - those soft, yellow leaves are a symptom of root rot. What you need to do now is take the orchid out of the pot, cut off all the black or soft roots with a clean tool, and repot it in fresh orchid moss or bark (don't reuse the same substrate). From now on, water when the substrate is almost dry to the touch, which might be every 10-14 days depending on your climate and light - most people overwater because they think orchids are rainforest plants that need constant moisture, but they actually prefer wet and dry cycles.
It's almost certainly overwatering. Phalaenopsis hate having their roots wet all the time, and watering every 5 days is way too frequent for most spaces. That moss you mentioned retains a lot of moisture, and combined with watering that often you're creating the perfect environment for the roots to rot. When the roots rot, the plant can't absorb water or nutrients and the leaves start to turn yellow and get soft. The first thing you need to do is stop watering for now and wait for the moss to dry out properly.
Next time you water, try the finger test: stick a finger about 2 cm into the moss and if it still feels moist, don't water. It probably needs water every 7 to 10 days, or even longer. Also, check if the pot has drainage holes; if it doesn't, that's also helping the water stay inside. Orchids like this prefer to dry out a bit between waterings.
If the problem is severe and a lot of leaves are soft, you can take the plant out of the pot and check the roots. If they're brown and soft, you'd need to cut them with something clean, let them dry out a bit, and repot it in fresh, dry moss. After that, be patient with the watering. The orchid will recover, but it's going to take some time.
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