Yellow leaves on Skimmia

It looks really quite decent and yes they are flower buds.
Evergreen plants mostly drop some leaves each year, so its quite normal for some of the old leaves to fall, probably late spring early summer.

I'd repot into a pot a couple of inches bigger when it finishes flowering around May next year.
Use ericaceous compost as you say, a JI ericaceous would be good, if you can find some, or better still, plant in the garden.

 

Thanks, that's really helpful. Thanks all.