I'll start by informing the community that i'm a rookie in the field of orchid care. I bought this white flowering orchid the day after Valentine's Day for a ridiculously low price of $5.99. I believe it was a mark down error by the seller, for which I could not pass up. I enjoyed the flowers for 2-3 months before it went dormant. I then set it outside for the entirety of the South Eastern summer under my leaky, damp, carport with very limited dirrect sunlight. The orchid loved it! It had all kinds of new leaves develop. I moved it inside once fall arrived and placed it in a southernly facing window. I did some reading on the subject and decided that It was time to repot to encourage budding.
It took off again and as I've watched the flower stems grow, inch after inch, day after day, my excitement has taken off too. But wait, what the heck is this?? A yellowing leaf and root rot on one side.. No! I can't believe it. I have immature buds at the ends of the stems and now i'm scared I may not get to enjoy the fruits of my laybor. Help! (I'll just go buy another one if this one doesn't make it but I'm a nurturer and would rather be proactive ;)
Medium: I used a moss medium instead of bark medium that it was originally housed in. Might not have been the best move when looking back at repotting but I never read anything that discouraged switching types of mediums. Plus, the moss was readily available in home.
It's lived inside a plastic pot within a pot. The outer stone pot does hold water so I usually water the plant by removing the inner plastic pot and drinch collected rain water through it. I wait to water until the medium feels dry to the touch before doing so. I suspect it's root rot that turned my leaf and surrounding roots but I'm not drowning my orchid in stagnant water for an extended period of time. Everything I've read mostly point to pooling water as the culprit for root rot and yellowing; could it be something else? Should I fertilize it? Should I use cenimon?

Here is orchid on Tuesday, which was 2 days ago, happy and green. I took this to show to a friend how green my thumb is turning- ha! I may have spoken too soon.

Normally I would never suggest that an orchid beginner uses sphagnum moss as a media. It is a media that beginners struggle with because of watering. Is it dry enough or should I wait? Is it still too damp? Plus the moss works much better with New Zealand Long fibred moss. Many people don't use the correct moss.
Additionally New growers can leave it too loose or pack it too tight. If you repotted using moss and the plant developed root rot shortly after, you most likely packed it too tightly.
Phalaenopsis like a bright location without any sunshine. They need to be watered well and then approach dryness before they are watered again.
Yellow leaves at the bottom are lost most often due to senility or old age. They don't last forever.
Lastly check out the forums here on "Supermarket Phalaenopsis" and others regarding their culture. I posted a thread last June I think on how I repot Phalaenopsis. Also check out the American Orchid Society website: AOS.org and look within at the top of the page pull down for their culture sheets. They are downloadable and printable pdf files. Get the one in Phalaenopsis Culture.

Oh don't grow it as a pot within a pot. This effects drying rate of the roots and can accelerate rot! Fertilize three or four times a year. No more then that. They are not heavy feeders and no benefit will be gained by using fertilizer.
Better off using cinnamon in an apple pie. Research is very mixed as to whether or not it helps to prevent rot or seal cuts from root removal. Good culture eliminates the need for any remedy!

Thanks, BigBill! I'll continue to do my homework. In your opinion, is it a bad idea to repot in a more suitable media at this point in development?

Oh Chello, you can repot whenever you want. Phalaenopsis are one orchid type that responds well to repotting.
New roots often appear within 4-6 weeks. If leaves become limp due to root loss, they often plump up in another 4-6 weeks after that.

Some people prefer to repot after flowers have died back. But I have over the years felt that you can repot them anytime especially in an emergency.

I don't think it looks all that bad. Yes, some rotting roots but also some fat green healthy roots. Don't worry about one older leaf yellowing as Phalaenopsis never have more than 3 or 4 at a time anyway.

I do have Phals in moss but, I let them dry out completely before watering. That clear plastic pot is how you will tell. Dry moss is a different color than wet moss. If you see ANY wet spots, don't water. You will see an abundance of new roots in no time.

It looks like you have done well. Look at all those future flowers! Please post photos when the flowers open.

Thanks again, Bill.
Daisyl, thanks for encouragement and watering tip. Will def. post the blooms! :))

Hey, my pleasure!

Yep, we're always happy to help. I was going to post a photo of two Phals I have still in moss but they have rooted to the inside of my decorative container.