Light Glitch inside a enclosed room

When I update into 19w02a yesterday, I found that my mob spawning tower was brighter than before, when I turn it on, there was nothing came out from my tower, than I go into the spawning room and I discovered my spawning area as bright as an open space in the day time.

I can't upload my pic and I tried my best to describe the issue, I hope you guys can fix it as soon as possible, thank you so much