Loosing Oncidium leaves though treated!

[kwarren]

I need some help quickly from any kind soul who knows what to do and will take a moment to instruct me.
My oncidium intergeneric plants are showing leap tip dieback, so I took the time to unpot them and soak for about an hour in a fungicide solution using "Manconeb".
Then I repotted in sterilzed pots and new bark. I cut offf the leaf tips and/or removed completly yellowed leaves before the submersion. That was two weeks ago.
Now I am noticing that the cut ends are starting to show the same light brown dieback and the oldest leaves are turning yellow quickly.
I am afraid of losing them. Am I using the wrong kind of fungicide? Do I actually have a virus problem?
I have many more catts and have had a slight problem with leaf rot in the past but the fungicide bath and new medium cured the problem along with better light and a little less watering.
Please someone help me. I would really appreciate it.