Why aren't the theme icons being applied after my update? (samsung j5)

[AC Question]

I did not know where else to ask for help since googling was unsuccessful. So I am using a Samsung J5 and it updated this afternoon, after the update was installed, my theme (mattblack) was applied but the icons were set to the default icons. i've tried restarting my phone/redownloading/reinstalling the theme but the icons are not being applied correctly. It also still applies default icons for other themes installed (space theme). I've also tried tinkering with the settings and the touchwiz home thing. Before the update it was working just fine. What should i do so that the theme icons would be applied correctly? This is my first time using an android phone so all of this is alien to me. Thank you for the help!
my phones adroid version is lollipop 5.1.1 baseband J500gxxu1apa2.