Why use `xargs` instead of `-exec`? And if you do need `xargs` (for example, for parallel processing with `-P`), it is recommended to use `-print0` with `find` and `-0` with `xargs` to avoid issues due to filenames.
(and agree re -print0/-0, it's absolutely essential)
In any case, OP was using `-n1` which means one file per invocation.