I agree you need to check the roots. Many Phalaenopsis orchids come in tighgly packed sphagnum moss and they need to be repotted. When you repot, pick a well draining plastic pot. A clear one is nice because you can see what the roots are doing. You want a pot that fits the healthy root ball snugly. You do not want to over pot. If it is planted in a clear plastic pot already (I can't tell if your plant is potted directly in that pot or is in another pot that is sitting in the clay pot) you might be able to reuse it if it fits the roots.
When you receive an orchid in bloom you don't know how old the blooms are so the flowers might not last very long. Your plants spike is turning yellow because it is done blooming. It might of prematurely died from many reasons including the fact that the plant is dehydrated from not enough watering or root rot from too much watering. They can also drop their blooms because of the environment change the plant went through, drafts, etc. But it probably was just the end of the plants bloom cycle.
The ariel root is silver because it is dry. They turn green when wet and silver when dry. The crack isn't that big of a deal. I have cracks in my roots and they still live. You should wet the ariel roots when you water and you can mist them in between waterings.
The biggest issue is the wrinkled leaves. This is because the plant is dehydrated either from under watering or root rot from over watering. If the top of the meadium is dry but it is still wet underneath don't water yet. There is still enough moisture for the plant. Many people use a kabob skewer to help them gage when to water. Take a skewer and put it in the meadium in the middle of the pot since this is where it dries out last. You want to water when the meadium is completely dry or almost dry. To check when to water, pull the skewer out and if it is wet don't water. If it is dry then water. If you are not sure if it is dry enough wait a extra day and check again. Most people kill their orchid by over watering not under watering. But don't let the Phalaenopsis stay dry for too long. Always keep the skewer in the pot and always put it back in the same place. When you water take the plant out of the decorative pot if it is in one. Many plants come planted in a plastic pot and then are set into an outer decorative pot. Put the plant under the faucet and water it thoroughly and then let it drain well. After it has drained you can put it back in the decorative pot but it can restrict air flow to the roots.
Welcome to Orchid Board! There is a thread called The Phal Abuse Ends Here and it has tons of great information about Phalaenopsis orchids. I recommend you read it. It is long but worth it! Here is the link and good luck!
http://www.orchidboard.com/community...ends-here.html