Sudden brown/soggy edges on Phal Leaves

[BrassCat]

Help! I've had this phal for three years and all has been good! Yesterday, I left it soaking for a few hours in my kitchen, returned and drained the water. I typically soak and have no issues.

This morning I noticed the edge/tip of one leaf was squishy and brown rotting, and the tip of the leaf below it appears brown as well! I have no idea what happened and I'm deeply worried.

I am planning to cut off the squishy upper part of the leaf and put cinnamon on the cut, and do the same to the leaf below it. But should I be doing something else?

Also any idea what could have happened? I'm worried this is something that could spread to my other plants, and I returned it to its place on the shelf that is very close to other orchids yesterday and it was there overnight. Thank you OB!