Sudden fungal/bacterial attack on my Vanda in spike

[Shadeflower]

Vanda's have got a bit of a reputation for being tricky unfortunately and I think this would be an example it seems.
From my limited experience I would say Vanda's need to adapt to their new environment first. The roots it previously grew are rarely suited for the new environment they get shipped to. I expect as standard for any new Vanda at mine to take one year to adapt to my climate and grow roots adapted to such climate. Then one more year to build up strength after having been set back with not yet adapted roots.
If you buy an orchid that was already being grown in your climate it makes a big difference to the health of the Vanda. When they are stressed they are susceptible and they will be highly stressed in the first year of owning them if they change their climate a lot so once one can get it past the first year then it should be able to continuously gain strength after that.

I am going to guess that stress will have played a big part for this newly acquired orchid. One cannot see the signs of stress when they occur but if one can help the orchid out and it recovers then the signs of recovery make what the signs of stress were quite obvious.
Hope it makes it.