Questions about RSU

Hi! While filing my tax return this year, I discovered that I owe a significant amount to the Federal. It appears that the main factor is the income from stocks. However, a considerable portion of them hasn't vested yet. For the vested part, I noticed that withholding has been applied. Does this mean that my stocks are either tax-paid or non-taxable? Are there any deductions or credits I can utilize to adjust my overall income?