Retirement tax questions

I am 69 now so I was older than 65 for 2018. In 2018, I was claiming 3 grandchildren as dependents and only 1 for 2019 so that would account for some of the increase. I was seeing on the 2019 form that some of the deductions that contributed toward my refund in 2018 were no longer being allowed for 2019(investment expenses). I will compare the adjusted gross income for both years first before doing a line by line comparison. I guess that I am having a "sticker shock" reaction. I knew that I was going to have to make an adjustment in my with holding amount due to fewer dependents. I just was not prepared for such a drastic change. I will look for any mistakes that I may have made. Thanks for your help