I'm sorry but think that your plant is, sadly, past the point where even the most seasoned grower would likely be unable to salvage anything. At some point the plant was severely overwatered, allowing the rot to set in. It's gotten far enough up the stem that most likely the core of growth (sorry about the scientific term) is rotting. My guess is that it developed when the plant was still in sphagnum; growers seem to love the stuff but in practice it's pretty hard to properly water a Phalaenopsis in it. Overwatering is simple in sphagnum.
Please don't let the loss of the plant deter you! There's not a sole on this board who hasn't lost a plant (or several) while learning the ins and outs of our hobby.
Hi Angela, welcome to OB! Unfortunately I agree that it is too late to save this plant. I only grow in bark mix, so I am not familiar with growing in LECA or sphagnum moss, but the right growing medium is whatever works.
Don't give up, it's a learning experience. I lost a few orchids myself when I first started growing orchids!
My guess is that it developed when the plant was still in sphagnum; growers seem to love the stuff but in practice it's pretty hard to properly water a Phalaenopsis in it. Overwatering is simple in sphagnum.