WHAT ARE THE DEFECTS IN VEDIC RECITATION ?

Vedas have to be properly recited by adhering to the svaras , matras and diction.
By not conforming to the injunctions (niyamas), one would get adverse effects.

There are six types of persons whose Vedic recitation is considered defective.


Six types of adhama pAthakas with reference to Vedic recitation:

(1) One who sings without following the svara niyamas
(2) One who chants very fast
(3) One who shakes the head while reciting
(4) One who recites the Vedas using a written text (book)
(5) One who does not know the meaning of Vedas
(6) One whose voice is not audible

gItI SIghrI Sirah kampI tathA likhita pAthakah!

anarthajnah alpakantasca shadete pAthakadhamah!!

WHAT IS THE REASON FOR BIRTH DEFECTS?

It is due to the prArabdha karma phala that one is born with deformity. Such a birth unfortunately one has to take in order to experience the sufferings.

According to Manu Smriti, one who does the karmas with whatever bhAvas, with the same type of SarIra, he experiences the fruits of his action .

yAdruSena hi bhAvena yadyatkarma nishevate!
tAdruSena SarIreNa tattatphalamupAsnute!!
--- Manu smruti

According to Sankha, one who kills a BrAhmaNa is born as a kushtha rogI, one who kills cow is born blind.

brahmahA kushthI ! goghnascAndhah !
--- Sankha

According to yAjnavalkya, one who steals annam gets afflicted with indigestion. one who steals oil is born as a cockroach.

annahartA AmayAvI syAt ! tailahrut tailapAyI syAt !
---- yAjnavalkya