What caused my return to decrease since 2018? Why do I owe the state $2k? Since being at my job since 2017 I haven't changed my paperwork.

It depends.  It could be for a number of reasons;  

Your particular state may have increased tax rates, or decreased exemptions and/or credits available?

You may have made more money which moved you to a higher tax bracket?

You may have answered a question(s) incorrectly?

You may not qualify for a deduction or credit that you did in a prior year?

Your filing status changed?

If you have not filed yet, please double check your Tax Summary. This will help you see your income, deductions, taxable income and you can compare it to 2018.  Choose Tools/Tax Tools/View Tax Summary.  See this link for more details:  View my Tax Summary before Filing  (The State Tax Summary will be just above the Federal Tax Summary in the black menu also)

Also, I recommend you go back through the interview questions, double check your W2 data entry and be sure it as well as your other information was entered correctly and you answered all questions correctly.