So it needs fertilization?

Yep. Thy simple things first. Sometimes mulch like wood chips will suck out nutrients, and sometimes soil get just imbalance of elements. Do you see it more than one plant? As in other perennials?

Others are fine, it's quite new hostabed. Maybe little in Spartacus also.

I had also a few that looked like this. Asked Renaat about it and he said it's because of the very warm spring, growing too fast to built up enough Chlorophyll and that a little bit of fertilizer is enough to mend it. They all look normal meanwhile...

Thanks Karin. It has really been very warm and hostas unfurled super fast. I think I just leave them alone and wait. Bed is so new and soil is fresh. I have fertilized few weeks ago.