please help flies and yellowing!!!! first cfl grow

my plantis in its 5th week of veg. i have 4-23w 5000k and 1-23w 2600k CFL
the box is 30x30x18
i noticed small and big flies are these a threat to my plants
how do i get rid of them?
why are my bottom leaves yellowing?


this is my plants last week when it was ok


the flies i found theres more

these are the leaves now

right now im cleaning out the room that the box is in hopefully that might help the flies
any suggestions will help thanks for reading!!!

Could be fungus nats, not the end of the world, a root drench with azamax should keep em in check..and are u sure ur not overwatering