\begin{tikzpicture}[node distance = 3.5cm, auto]
  \node [start] (init) {Mix \qty{50}{\gram} flour + \qty{50}{\gram} water, stir};
  \node [block, right of=init] (wait2) {Wait\\ \qty{24}{\hour}};
  \path [line] (init) -- (wait2);
  \node [block, below of=wait2, node distance=3.5cm] (feed) {\qty{10}{\gram} of previous day + \qty{50}{\gram} water + \qty{50}{\gram} flour, stir};
  \path [line] (wait2) -- (feed);
  \node [block, below of=feed] (discard) {Discard the rest};
  \path [line] (feed) -- (discard);
  \node [decision, right of=feed, node distance=3.5cm] (decide) {Is good?};
  \node [decision, above of=decide, node distance=3.5cm] (timeout) {Less than 10 feeds?};
  \node [fail, right of=timeout, node distance=3.5cm] (discard2) {Batch failed};
  \path [line] (timeout) -- node{no} (discard2);
  \path [line] (timeout) -- node{yes} (wait2);
  \path [line] (feed) -- (decide);
  \node [success, right of=decide, node distance=3.5cm] (use) {Ready to use};
  \path [line] (decide) -- node{no} (timeout);
  \path [line] (wait2) -- (feed);
  \path [line] (decide) -- node{yes} (use);

  \node [start, below of=discard, left of=discard] (start_n) { Start with Initial Mixture };
  \node [block, right of=start_n, node distance = 3.2cm] (wait_n) { Wait\\ \qty{24}{\hour} };
  \node [decision, right of=wait_n, node distance = 3.2cm] (readycheck_n) { Ready? };
  \node [block, below of=wait_n, node distance = 3cm] (feed_n) { Feed the Mixture };
  \node [decision, right of=feed_n, node distance = 3.2cm] (limitcheck_n) { Failed? };
  \node [fail, right of=limitcheck_n, node distance = 3.2cm] (abort_n) { Discard All, Start Over };
  \node [success, right of=readycheck_n, node distance = 3.2cm] (final_n) { Done };

  \draw [line] (start_n) -- (wait_n);
  \draw [line] (wait_n) -- (readycheck_n);
  \draw [line] (feed_n) -- (wait_n);
  \draw [line] (readycheck_n) -- node { No } (limitcheck_n);
  \draw [line] (limitcheck_n) -- node (feedok_n) { No } (feed_n) ;
  \draw [line] (limitcheck_n) -- node { Yes } (abort_n);
  \draw [line] (readycheck_n) -- node { Yes } (final_n);

  \node [below of=feedok_n, node distance=2cm, align=left] (details2) [shape=rectangle,draw,fill=maingray]{
    For the \emph{Initial Mixture}, mix \qty{50}{\gram} flour/\qty{50}{\gram} water.\\
    The Mixture is \emph{Ready} when it has
    \emph{grown}, has \emph{bubbles}, and \emph{smells}
    vinegary/yoghurty. \\

    The Mixture has \emph{Failed} when you
    have fed it too many (\eg~10) times without success.\\

    To \emph{Feed the Mixture}, discard all but \qty{10}{\gram}, mix in \qty{50}{\gram} flour and \qty{50}{\gram} water.
  };
\end{tikzpicture}