Space after macro involving a TikZ picture

I wrote a macro to print linear combinations and related things using TikZ (pgffor really, but I need TikZ for other things in a big document). Here’s a MWE:

documentclass[11pt]{article}

usepackage{tikz,spalign,xspace,amsmath}

newcommandlincomb[3]{% 3args: list of coeffs, vector symb, operation
%   begin{tikzpicture}
    tikz{
        foreach x [count=j] in {#1}{
            ifnumj=1
                $x{#2}_{j}$
            else
                ${#3}x{#2}_{j}$
            fi
        }xspace
%   end{tikzpicture}
    }
}


begin{document}

begin{equation}
    spalignmat{0.7;0.5;0.1}={lincomb{0.7,0.5,0.1}{mathbf{e}}{+}}quad
    ;text{and}:
    spalignmat{0.1;0.5;0.7}=lincomb{0.1,0.5,0.7}{mathbf{e}}{+}
end{equation}

$lincomb{a,b,c}{f}{-}$ and then some text.

begin{tikzpicture}
    foreach x [count=j] in {a,b,c,d}{
        ifnumj=1
            $x f_{j}$
        else
            $+ x f_{j}$
        fi
    }
end{tikzpicture} and then some text

end{document}

The output is at the end. What I want is to have proper spacing between two of these. As you can see, I even tried using the code as a standalone piece of text, but got the same result; I also tried using the tikzpicture environment, but nothing changes. After seraching I’ve seen many questions asking to remove space after a tikzpicture, but I want to add it. As you can see also, xspace doesn’t work here either. Thanks in advance!!

documentclass[11pt]{article}

usepackage{tikz,spalign,amsmath}

newcommandlincomb[3]{% 3args: list of coeffs, vector symb, operation
%   begin{tikzpicture}
%    tikz{
        foreach x [count=j] in {#1}{
            ifnumj=1
               x{#2}_{j}
            else
               {#3}x{#2}_{j}
            fi
%        xspace
%   end{tikzpicture}
        }
}

begin{document}

begin{equation}
  spalignmat{0.7;0.5;0.1}={lincomb{0.7,0.5,0.1}{mathbf{e}}{+}}quad
    ;text{and}:
  spalignmat{0.1;0.5;0.7}=lincomb{0.1,0.5,0.7}{mathbf{e}}{+}
end{equation}

$lincomb{a,b,c}{f}{+}$ and then some text.

end{document}