Two Types Of Fifths

Regarding one who redeems his own hekdesh it says (27:19) וְאִם־גָּאֹ֤ל יִגְאַל֙ אֶת־הַשָּׂדֶ֔ה הַמַּקְדִּ֖ישׁ אֹת֑וֹ וְ֠יָסַ֠ף חֲמִשִׁ֧ית כֶּֽסֶף־עֶרְכְּךָ֛ עָלָ֖יו וְקָ֥ם לֽוֹ.  In possuk 31 regarding redeeming one’s maser sheni it says וְאִם־גָּאֹ֥ל יִגְאַ֛ל אִ֖ישׁ מִמַּֽעַשְׂר֑וֹ חֲמִשִׁית֖וֹ יֹסֵ֥ף עָלָֽיו.  There is a difference in how the Torah refers to the owner of the hekdesh vs. the owner of the maser sheni.  When it comes to hekdesh it calls him/her the מקדיש but when it comes to maser shni s/he is called the owner, ממעשרו.  The reason for this difference is that when it comes to maaser, one is defined as the owner.  On the other hand, once someone makes something hekdesh, it is out of his/her possession and he is refereed to merely as the מקדיש.  This is illustrated by this Or Sameach in Arachin 7:2.