Phal leaves suddenly turning yellow & spongy
 

I received a beautiful kaleidoscope phal in bloom from Mom a week ago. Had a small sunburn patch on one of the lower leaves -- not a big deal, however, I'm alarmed at the sudden softening & yellowing of the 2 newest leaves which up until a week ago had been firm and green. The situation is changing fast -- last week the plant seemed OK and now I'm afraid it is terminally ill :((

Hoping someone can tell me what's the problem and if there's anything that can be done. Or how to avoid this happening to other chids in the family. (already isolated this one to avoid spreading diseases)

potted in bark with lots of air circulation

You had the right idea isolating that one. I'm no pro but looks like a possible bacterial infection. Lets see what the others say.

I don't know what exactly it is but I would cut the leaves off and use a cotton ball and alcohol to try to disinfect/dry the Rest of the plant until you can get ahold of something better. Don't use it on flowers or roots, it dries too much and kills them. Here is a link to an Orchid Society's website which I use as well as the diagnostic table at Cloud's Orchids to solve all my fun fungual and bacterial orchid problems.
Orchid Pests, Orchid Diseases

---------- Post added at 05:03 PM ---------- Previous post was at 05:00 PM ----------

Here is Cloud's Orchids' site: Diagnosing Orchid Problems
These are two good links to keep bookmarked!

It looks like the worst leaves are the newest. Could water have settled in the crown?
Try to water before mid-day so that they have time to dry before night. I sometimes take a paper towel and blot up any water sitting in the crown.
King-of_Orchid-Growing has some pictures of how phals grow in the wild- what we would consider "upside down". That way the water in their naturally wet environment can't cause crown rot.
Welcome to OB, by the way!

Connie - Just FYI - not al species Phals grow in a donward fashion. There are many, if you mounted them that way would essentially make a u-turn and start growing upwards much like those in cultivation. Off the top of my head Phal pulchra is a good example.

These leaves look burned also. Cut the affect leaves back to healthy tissue and pull it away from the sun :)

that looks like erwinia or pseudomonas. if it is then your plant should be gone in a few days. its so close to the crown it may not survive. try the methods everyone suggested and it may survive but id just look for a new plant is it may take a long time to recover. good luck

I didn't know that. Mine (almost all hybrids) seem to want to grow down if I let them.

sunburn sometimes takes a couple days to fully show effects....i believe it looks like sunburn....keep it dry for a while and trim off the affected leaves....treat with cinnamon and hope the crown isnt destroyed.....if it is, you might get keikis, but its going to be years before the plant recovers if at all....gl

update: 'Phal leaves suddenly turning yellow & spongy'
 

Thanks to all who posted; the picutures in the links were helpful -- I'm thinking its either erwinia or a possible thermal injury. I looked up the temperatures on the day my mom brought it to my house and found it had been ~10 F

Update:
Less than 36 hours after my original post, the leaf 2nd from the crown spontaneously dropped off the plant. In attached photo 'dropped_leaf' you can see the healthy tissue to the left and the diseased/damaged part closest to the monopodial stem.

Today, I cut the diseased/damaged parts of the crown leaf back as far as I dared and treated all open wounds with cinnamon. In the attached photo 'cut_leaf' you can see yellow had begun to turn black.

Is there any chance this was caused by exposure to cold? Guess I'll know in a few more days if the patient is going to survive.