Bee Box question

[Susie]

Apologies if this is the wrong part of the forum for this question, but I think that the people who are likely to know the answer are more likely to frequent the insects section.

I have some bee boxes for solitary bees in the garden. Two of these are a couple of seasons old now and quite a few of the cells are blocked because the incumbants were parasitised or failed to emerge for some other reason.

So, my question is, should I clean out these tubes or do I have to buy and/or make more bee boxes to replace them?

Many thanks,

Susie