I have these sunken spots on the underside of phal Cassandra leaves. They are colorless and don't change or spread. I have been monitoring it for over a month. They affect only two older leaves and are not visible from the top. What can it be and how bad is it?
Agreed with Cym lady. If it isn't spreading, mechanical/insect/etc are possible, but has probably subsided. I'd keep monitoring it, but wouldn't worry too much, as it looks very healthy (new leaf and good roots).
I'd vote mechanical issue too, eventually a bit of localized cold or an insect very partial at his dinner… As long as it's not evolving/spreading, you're safe don't worry. And it looks a fit chap your phal.
Thank you evrybody. I feel better now. Maybe it was some kind of pest munching on my leaves before plant got here. I will continue monitoring. I was just worried that it could be some type of virus where there is nothing you can do to cure it.