Annpurna is right. Rama & Lakshman went to Vishwamitra's ashram in royal garb, not vanvasi clothes. Unlike in their vanvas, they went there specifically to kill Tardka & her companions, not for becoming hermits. All those events, including the liberation of Ahalya, took place w/ them in royal clothes.
Showing them in vanvasi clothes has just spoilt a lot of this.