Tikz arrows to equation not showing up

I would like to add arrows that point to different parts of an equation in a beamer presentation. I would like to highlight them iteratively. I used this question to attempt this, but the arrows don’t appear at all. I tried excluding the {small ... }% environment but it did not fix it, not did getting rid of the highlighting or messing with the distances. Thanks for any help.

documentclass[12pt,dvipsnames]{beamer}

usetheme{metropolis}

usepackage{textgreek}
usepackage{tikz}

newcommand{tikzmark}[1]{tikz[baseline,remember picture] coordinate (#1) {};}

usepackage{booktabs}
usepackage[scale=2]{ccicons}
usepackage{amsmath}
usepackage{mathtools}
usepackage{amssymb}
usepackage{subcaption}
usepackage{caption}
usepackage{multicol}
usepackage{minted}
usepackage{hyperref}
hypersetup{
    colorlinks = false,
    linkbordercolor = {blue}
}

title{Something Interesting}
author{Name}
date{today}

begin{document}
maketitle

begin{frame}[fragile]{Title}

{small  
begin{equation*}
textrm{
Ytextsubscript{gt} =
textbetatextsubscript{0} +
alert<2>{tikzmark{V}textbetatextsubscript{1} Atextsubscript{1}} +
alert<3>{tikzmark{Vp}textbetatextsubscript{2} Btextsubscript{2}} +
alert<4>{tikzmark{Vt}textbetatextsubscript{3} Ctextsubscript{3}} +
alert<5>{textgammatextsubscript{4} Xtextsubscript{4}} +
textepsilontextsubscript{...}
}
end{equation*}

begin{tikzpicture}[overlay,remember picture]
    node (Ve) [below of = V, node distance = 4 em, anchor=west]{footnotesize textsf{Distribution volume}};
    draw[<-, in=180, out=-90] (V.south)++(.25em,-.5ex) to (Ve.west);

    node (Vpe) [below of = Vp, node distance = 3 em, anchor=west] {footnotesize textsf{Volume water in plasma}};
    draw[<-, in=180, out=-90] (Vp.south)++(.25em,-.5ex) to (Vpe.west);

    node (Vte) [below of = Vt, node distance = 2 em, anchor=west] {footnotesize textsf{Volume water in tissue}};
    draw[<-, in=180, out=-90] (Vt.south)++(.25em,-.5ex) to (Vte.west);

end{tikzpicture}
}%

end{frame}
end{document}