Natural age or yellowing?
 

I have had this plant for a few months and within the last week it's lost one or two of it's very bottom leaves. And now this leaf is turning yellow too. The overall plant looks good, has a lot of new growth (4 new shoots). Should I be worried or is it natural aging?

Cymbidium leaves do fall off as they age. They gradually lose their green colour, turn yellow and then break off a few inches above the psb. This is all quite natural and here in the UK it is happening to several of my cyms now.

Only you can see what is happening to your plant in situ but unless it is losing a lot of leaves I suspect this is quite normal.