Foaming of distilled water

[opal]

I soak my orchids in distilled water once a week, or as needed. Most of them are in clay pebbles, and since I have them for a while, I soak them in the same water one by one. So no problem there. But I have 4 orchids in different media: paphs are in their orchids mix of everything and I soak them separately and I have Onc. Sharry Baby and onc hybrid in original media I brought them home with. What worries me is Sharry Baby. Every time I soak it, for the past 3 years, when I take it out, the water is foamy (brownish I get it - wood decomposing). It really doesn't matter whether I soak it first or last, the water will end foamy. It really confuses me. This orchid had some snails problem in the past. Could it be, there are still some snails hiding deep down there making distilled water foam? It's confusing, distilled water should be neutral with no chemical reactions and surely it doesn't react with any other media I have. Any advice/experience with such thing? I took out all the media I can reach through roots, but mostly it's stuck on roots and I'm afraid to damage them all if I push it.