rust on dies

[Big joe]

I have some old Lee dies that have served me well for years. I haven't used them for maybe 5-6 years and I noticed they have some rust on them-inside and out. This kinda surprised me, living in Utah, moisture isnt typically a problem. Anyway... how much of a problem is this? Should I replace them, can I clean them, does it even matter? If you can give me some info I'd be abliged.

Thanks for your info...