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Hovering the mouse over the icons reveals their meaning:

That indicates you've built a smart preview for the photo (Library > Previews > Build Smart Previews) and LR doesn't have access to the original, so it's using the smart preview. See here for how to deal with such missing photos:
https://www.lightroomqueen.com/lightroom-photos-missing-fix/

That indicates the metadata for the photo stored in the catalog is newer than what's stored on disk. Options:
- Ignore it.
- Do Metadata > Save Metadata To File.
- Set the option Catalog Settings > Metadata > Automatically Write Changes To XMP.
- Uncheck the option View > View Options > Grid View > Cell Icons > Unsaved Metadata.
