Im wondering why my refund went down after filing my third return. My income is still below the $21,000 mark so I'm confused

Your refund went down after entering a second and third W-2s, this is because we start you off with the full standard deduction, which we subtract from the income you’ve entered so far. You don’t get this deduction with each W-2 you enter, just the first one. This means your other W-2s will appear to be taxed more, but what’s really happening is that you’re getting a more accurate picture of your income.

Your refund also depend on the amount of taxes that your employers withheld during the year. Keep in mind that the "refund monitor" does not mean anything until everything has been entered.