The vṛddhi is not substituted for the vowels of jan 'to produce' and vadhe before the Aorist sign ciṇ and the kṛt affixes with an indicatory ñ or ṇ ,
As अजनि and अवधि with चिण्, and जनकः and वधकः (with ण्वुल्), प्रजनः, वधः ॥ This rule refers to the separate and the distinct root वध and not to the substitute of हन् ॥ This we see in the line भक्षकश्चेन्न विद्यते वधकोऽपि न विद्यते ॥ The form from हन् will be घातकः ॥ Moreover the substitute वध ends with अ i.e. it is of two syllables 'badha', and as such it also does not admit Vriddhi. (See 2.4.42). The prohibition refers to चिण् and krit-affixes, therefore not here, as जजान गर्भं महिमानमिन्द्रम् ॥,