Looks like fungus or bacteria, but it could also be a virus. I googled a bit to see if there were phal who had the same symptoms as yours.
This one and
this one do. If you want to know specifically what it is, you shoud have a lab test it and do a virus test. If it's a virus, then the progression of symptoms should be slow. If it's fungus or bacteria, it will be way faster.
My advice is : 1 - Whatever it is, it seems highly infectious so separate all plants showing symptoms from the ones that seem healthy. 2 - If it is a virus, there's nothing you can do if symptoms appear, the plant will eventually die. 3 - If it's fungus or bacteria, it's fungicide/desinfectant time! Try something that kills a large spectrum of micro-organisms.
I hope this helps.