I have been growing orchids for about 8 years now with success. I have always used my tapwater sometimes mixing with small amounts of rainwater. About 3 weeks ago I had about 40 phals in spike, bud or bloom. After watering and within days all flowers except those with very heavy substance dried up, buds blasted and now I am getting yellow leaves on many of my collection catts, phals etc. I am at my wits end to figure out what the cause could be. I have called the water treatment plant and they claim they have not changed anything. I am planning to have my water tested to see if anything caustic shows up but have never had it tested before so I have no baseline. I have noticed that my commodes are not getting dirty as before I had to clean them every few days. I don't know what this could mean. I have now ordered an ro system but am worried what will happen til I receive it and get it installed. Any thoughts would be greatly appreciated.

Sounds like a nightmare. I hope you get it fixed. I don't have any ideas.

It's probably in the water as you stated. Perhaps you can use rainwater or distill water for the time being until you get your water test result. Some city use chloramine for water treatment and high concentration is not good for tropical fish or plants. There are specific membrane for RO to remove chloramine

Could the plants been exposed to some type of gas or cold temps (water or air)?

It sounds similar to my problem. During the extremely low temperatures in January my water tank under the staging dropped to only about 1c. Temperatures at staging height and above remained normal even with continuous fans running, but the thermostat was foolishly set for staging temps. I dunked my mounted plants as normal before realising what was going on, within a few days the roots chilled drastically causing them to die and completely dry out, the result was the plants stopped getting water via the roots, spikes dried out completely, leaves shriveled and completely dried out. I lost a lot of plant species, some may recover very slowly but probably won't flower again for a few years. Some that are recovering have half a leaf healthy while the other half of the leaf is crispy.
I won't be caught out again, I now run aquarium heaters in my water tank and keep the water at 19c (C. 65f).
Bill.

It's definitely not cold water. I was having some furnace problems but even if there was some escape of carbon monoxide it was a very small amount. What kind of gases would cause that kind of flower collapse so quickly? There was not enough to trigger our carbon monoxide detector or smell. I only hope I do not loses plants over it. They will bloom again next year, I hope but it sure is discouraging

I don't use gas to heat, so have no experience with it. However, I have heard stories of greenhouses that are gas heated having the exhaust clogged an producing symptoms similar to yours virtually over night. I don't even know if CO is the problem or someother gas. Perhaps someone who heats their greenhouse with gas can provide more information than me. But, at this point, that sounds like it's the problem.

Orchids are famous for their sensitivity to byproducts of incomplete burning of hydrocarbon fuels.

My main heat is with bottled-gas burners, but I've never had that problem. I have heard of one or two people in the UK suffering from bud-blast due to burners not burning cleanly. Usually a good service of the gas appliance, paying particular attention to the burners being well cleaned, solves the problem. Normally the problem causes bud-blast though rather than flowers/spikes drying out.
Bill.