Tikz: Using relative positioning and foreach variables

Question

I want to generate a picture that replicates itself and slowy fades out. For that i plan to use a foreach statement and redraw the picture to its rigth.

How can i use the foreach variable to position my replicated pictures.

Here is a minimal example that illustrates what i want. The remaining job in the minimal example is to somehow use \x to create the names for relative adressing the nodes during redraw.

\begin{tikzpicture}[
  item/.style={draw=black!#1, thick, text=black!#1, minimum width = 60},
  label/.style={text=black!#1, right},
  action/.style={black!#1, ->, thick},
  downfrom/.style={below = 0.5 of {#1.south}, anchor=north},
  rightfrom/.style={right = 0.5 of {#1.north east}, anchor=north west}
]

\foreach \x in {100}
{
    \node [item=\x]                     (first100) {first};
    \node [item=\x, downfrom=first100]  (second100) {second};
    \path[action=\x](first100) edge node [label=\x] {a} (second100.north);
}   

 \foreach \x in {67}
{
    \node [item=\x, rightfrom=first100] (first67) {first};
    \node [item=\x, downfrom=first67]   (second67) {second};
    \path[action=\x](first67) edge node [label=\x] {a} (second67.north);
}   

 \foreach \x in {34}
 {
    \node [item=\x, rightfrom=first67] (first34) {first};
    \node [item=\x, downfrom=first34]  (second34) {second};
    \path[action=\x](first34) edge node [label=\x] {a} (second34.north);
 }  

\end{tikzpicture}

What i want to write but i dont know how would look like this:

\begin{tikzpicture}[
  item/.style={draw=black!#1, thick, text=black!#1, minimum width = 60},
  label/.style={text=black!#1, right},
  action/.style={black!#1, ->, thick},
  downfrom/.style={below = 0.5 of {#1.south}, anchor=north},
  rightfrom/.style={right = 0.5 of {#1.north east}, anchor=north west}
]

\foreach \x in {100, 67, 34}
{
 \node ???
 \node ???
 \path ???
}   

\end{tikzpicture}

Answer 1

Something like this?

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}

\begin{tikzpicture}[
  item/.style={draw=black!#1, thick, text=black!#1, minimum width = 60},
  label/.style={text=black!#1, right},
  action/.style={black!#1, ->, thick, draw},
  downfrom/.style={below = 0.5 of {#1.south}, anchor=north},
  rightfrom/.style={right = 0.5 of {#1.north east}, anchor=north west}
]

\path coordinate(last);
\foreach \x in {100,67,34}
{
  \node[item=\x, rightfrom=last, alias=last](first\x){first};
  \node[item=\x, downfrom=first\x](second\x){second};
  \path[action=\x](first\x) edge node [label=\x] {a} (second\x);
}    
\end{tikzpicture}

\end{document}

Answer 2

You can scope the drawing and shift it each time to the right.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\begin{document}
\begin{tikzpicture}[
  item/.style={draw=black!#1, thick, text=black!#1, minimum width = 60},
  label/.style={text=black!#1, right},
  action/.style={black!#1, ->, thick},
  downfrom/.style={below = 0.5 of {#1.south}, anchor=north},
  rightfrom/.style={right = 0.5 of {#1.north east}, anchor=north west}
]

\foreach \x[count=\xi from 0] in {100,64,37}
{
\begin{scope}[shift={(3*\xi,0)}]
    \node [item=\x]                     (first\x) {first};
    \node [item=\x, downfrom=first\x]  (second\x) {second};
    \path[action=\x](first\x) edge node [label=\x] {a} (second\x.north);
\end{scope}
}   

\end{tikzpicture}

\end{document}