How to define the default vertical distance between nodes?

How to define the default vertical distance between nodes?

Use positioning can control the individual vertical position of nodes. But is there any way to control the default vertical spacing?
\begin{tikzpicture}[node distance = 1cm, auto]
    \node [block] (1st) {1st};
    \node [block, right of=1st]  (2nd1) {2nd1};
    \node [block, above=0.7cm of 2nd1] (2nd2) {2nd2};
    \node [block, below of=2nd1] (2nd3) {2nd3};
    \node [block, right of=2nd1] (3rd1) {3rd1};
    \node [block, above of=3rd1] (3rd2) {3rd2};
    \node [block, above of=3rd2] (3rd3) {3rd3};
    \node [block, below of=3rd1] (3rd4) {3rd4};
    \node [block, below of=3rd4] (3rd5) {3rd5};
    \path [line] (1st) -- (2nd1);
    \path [line] (2nd1) -- (2nd2);
    \path [line] (2nd1) -- (2nd3);
    \path [line] (2nd2) -- (3rd3);
    \path [line] (2nd1) -- (3rd1);
    \path [line] (1st) -- (2nd1);

\end{tikzpicture}
Like this. I changed the vertical position of 2nd2 but others remains. Do I have to add individual vertical spacing control of every nodes?