Consider the following quantified proposition:
$$\exists x\ : R(x) \land T(x) $$
where $R(x)$ is 'x likes to paint in red,' $T(x)$ is 'x likes to live on a tree,' and $x$ is the domain of all monkeys.
Is the following a valid restatement of the above expression?
$$\exists x\ : R \land T $$
If $$ M =\mbox{the set of all monkeys} $$ $$ R(x) =x\ \mbox{likes to paint red} $$ $$ T(x) =x\ \mbox{likes to live on a tree} $$ Then I'd write it like this $$\exists x\in M : R(x) \land T(x) $$ But if you choose to write $$\exists x\in M : R \land T $$ Your forcing the reader to assume that $x$ is the parameter of both $R$ and $T$, which is okay since $x$ is the only variable in this case.
So to directly answer your question, yes it's valid. My preference is to be clear, but to each their own.