We already have have a script implemented to carry forward the utms to other links on the LP but that doesn't seem work for the TY Page.
Use the code from the JS pane here:
MktoForms2 :: Append current querystring to TY URL v1.0.2
As always, on a Marketo LP, place just before the closing </body> tag; on a non-Marketo page, place anywhere after the embed code.