With how the outskirts of the holes are somewhat white.
You have something munching away. Simply put. You can't prevent all things that creep and crawl from getting into your tent.
Any dead growth. Clean all up. As it attracts pests. I wouldn't worry about it too much. Its most likely just an oddie and will die off.
Maybe lay a few yellow sticky traps around and see what you catch.
Although its normal its still poxy annoying..
Good Growing & Join the community.