Lighting Glitch: it seems that all of the blocks are under sky light, and pressing F3 on them shows 15 sky brightness. I tested this in a single player world and it doesn't seem like a feature. It seems to randomly affect chunks.
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Update: This is what happens when I log in and relog (running on a server, tried restarting it but problem persisted)
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Update 2: Found this glitch happening deep underground; the client and server light are both 15 sky.
violine1101
Duplicate of MC-149518