a. continued observation and then repeat step #2
b. treatment with copper based fungicide (Phyton 27 or other) and then #2.a.
c. cutting off the leaf well into healthy tissue and then #2.a.
So at any point you can change your diagnosis and then react how you see fit to treat the current condition.
The information you get from observing is very valuable.
Fast moving soft or edematous lesions that leave behind brown atrophic spots are bacterial and possible fungal.
Slow moving are more likely fungal but can also be bacterial.
Spots that don't really increase much in size and simply become atrophic without any soft areas are likely sunburn.
This could also be a previously treated condition/infection
This still looks a lot like sunburn to me.
Standing water on a cattleya plant on a bright day will certainly burn it.
However, the injured leaf can get a secondary infection! Thus you must be on guard..."flexible"
PS. I like Phyton 27 because it treats bacterial AND fungal disease with the exception of just a few fungal culprits left out
However, I recently learned it takes about a week for a copper based fungicide to become effective and was recommended to also concurrently treat with Physan which is broad spectrum