Pixelated formula with amsmath

Question

I just realized that my formulas become pixelated when I zoom-in on them and I don't know the reason. They look like this:

Here is a tiny MWE:

    \documentclass{thesis}

\usepackage[authoryear,round]{natbib} 
\usepackage{afterpage}
\usepackage[spanish]{babel}
\decimalpoint
\usepackage{wrapfig}
\usepackage{array}
\usepackage[T1]{fontenc}
\usepackage{garamondx}  %Font type
\usepackage{doi}
\usepackage[utf8]{inputenc}  % For accents marks on spanish
\usepackage{verbatim}  % Needed for the "comment" environment to make LaTeX comments
\usepackage{vector}  % Allows "\bvec{}" and "\buvec{}" for "blackboard" style bold vectors in maths
\usepackage{pdflscape} % for rotating pages
\usepackage{lscape} % images as full page
\usepackage{enumerate} % for listing
\usepackage[graphicx]{realboxes} % for rotating tables and resizing
\usepackage{multirow} % multirows for tables

\usepackage{amsmath} % Equations
\usepackage{bm} % Equations

\begin{document}

\begin{multline}
\label{eqn:eqn4}
\boldsymbol{P(Kbar) =} 4.76Al - 3.01 - \left ( \frac{T(^{\circ}C) - 675}{85} \right ) \times [0.53Al + 0.005294 \times (T(^{\circ}C) - 675)]
\end{multline}

\end{document}

I've already installed cm-superfrom MPM and tried solutions like this and others. Should I change the math font or something?

Thanks!