First of all don't fell like you are necessarily to blame. If the plant is in spagnum, most of the time they are doomed. It's important when you buy a new orchid to go ahead and repot it. Phals are pretty forgiving and as long as you are gentle and do not break roots it'll do just fine. Buy a bag of the phalaenopsis bark mix at your local hardware store or big box store and repot. I would guess the knot of compacted stuff in the middle is killing your plant. It sounds like you are doing right with the watering. If you still feel unsure, you can try the wood stick in the mix to check how dry it is. Put the stick to your cheek...if it's cold and damp don't water. If the stick feels warm and dry it's time to water. I try to encourage people to repot before they give up and say orchids are too hard. Many times the plants aren't expected to live and are potted to last only through the flowering. Good luck with your next orchid...it may also be you haven't found the right kind for your care. Sometimes a person that cannot keep a phal alive does great with cattleya. Hope this helps.