Sudden leaf issues

[Jak]

Hello all,

I gifted my friend with a partition of my cymbidium 2 years ago, and it has been doing very well, new growth, blooming.

Today he messaged me, that between waterings the damage you see in the pictures happened (50% of the leaves are affected)... He is ocd about plants (the reason I gave him the partition), so I am sure this damage was not there at the last watering. The only things out of the ordinary were:
- watering was done in 10 days not 7 as usual
- fertilised as normal (1x month)
- we went into abrupt autumn (the plant is inside tho)

I hope this has a solution, as I have never experienced this, and am at whit's end :-(

Thank you for any info,
Jakub