Orchid leaves get watery and like a jelly, that's how it starts...

[Beaveljeez]

I have rescued a couple orchids from Lowes and Home Despot that shortly after the leaves start to get this jelly like feel to them, it works its way down the leaf and then to the stem, then it's like the whole plant becomes like that and just melts. I was wondering if there is anything I can do to prevent this from happening or treat it. Please help. Thank you.