I'm going to have to throw these away aren't I? Help?

[Carouselfish]

My favourite bowls! Not expensive but hard to find design now. Two of them have got black mould on the bottom. No idea how. They are jn constant use, washed up the same day. Some rammikins I kept in the same cupboard had this happen to them a couple of months ago and I put them in the bin. Nothing else in cupboard or other cupboards have this problem! Any idea why or best way to get rid of it? I've scrubbed with a wire ball to no avail.

Have you used mould and mildew remover?

Quick spray of flash bleach.

Really?

I'm not sure I'd have noticed and if I did I have to say it wouldn't have occurred to me to throw them away

Is the picture misleading?

White vinegar?
Bleach?
Sandpaper v fine?

It looks like mould has got in where there isn't any varnish.

I'd give mould remover a go like Palavah suggested or would clean it with some bleach.

Expect @Lindy2 is right about the gaps in varnish. It seems quite ingrained as it sort of bleeds black colour when I scrub it but doesn't go away. Wonder if this means rest of crockery is just better varnished? I'll try the natural remedies first before bleach and then if it goes, re-varnish.
Admit I am a bit of a trigger-happy binner.

I sometimes get this on the underside of the cat bowls (they are partially glazed), so always make sure they are properly air dried before putting away.