Did it get cold? I have similar leaves in a brassavola that was left out in cold ( temps Over 40 ). It did not have good roots yet as it was newly acquired. Try watering with Epsom(1 tablespoon a gallon ratio- weekly).
The fact that the older leaves aren't showing it makes me think environmental/cultural/ or nutritional.
I haven't had a ton of experience w/virus but what I have seen has shown up in the older growths first. W/out testing you will likely never know for sure.
BTW - I've also seen/heard (OFTEN!) where plants that look sick test perfectly fine and those that look perfectly fine end up testing positive for virus.
So it seems no definitive answer unless I do a virus test which i will not. I will keep it quarantined and if things get worse or it seems to weaken then i will replace it. Funnily enough the new growth seems quite strong and robust apart from the colour.