Arguments against the Apocrypha
1. There is not sufficient evidence that they were reckoned as canonical by the Jews anywhere.
2. The LXX design was literary, to build the library of Ptolemy and the Alexandrians.
3. All LXX manuscripts are Christian and not Jewish origin. With a 500 years difference between translation and existing manuscripts. Enough time for Apocryphal books to slip in.
4. LXX manuscripts do not all have the same apocryphal books and names.
5. During the 2nd Century AD the Alexandrian Jews adopted Aquila’s Greek version of the OT without apocryphal books.
6. The manuscripts at the Dead Sea make it clear no canonical book of the OT was written later than the Persian period.
7. Philo, Alexandrian Jewish philosopher (20 BC-40 AD), quoted the Old Testament prolifically, and even recognized the threefold classification, but he never quoted from the Apocrypha as inspired.
8. Josephus (30-100 AD.), Jewish historian, explicitly excludes the Apocrypha; numbering the books of the Old Testament as 22 neither does he quote the apocryphal books as Scripture.
9. Jesus and the New Testament writes never once quote the Apocrypha, although there are hundreds of quotes and references to almost the entire book of the Old Testament.
10. The Jewish scholars of Jamnia (90 AD) did not recognize the Apocrypha.
11. No canon or council of the Christian church recognized the Apocrypha as inspired for nearly four centuries.
12. Many of the great fathers of the early church spoke out against the Apocrypha---for example, Origen, Cyril of Jerusalem, and Athanasius.
13. Jerome (AD 340-420) The great scholar and translator of the Latin Vulgate rejected the Apocrypha as part of the canon.
14. Not until 1546 AD in a polemical action at the counter-Reformation Council of Trent (1545-63), did the apocryphal books receive full canonical status by the Roman Catholic Church.
(http://www.truthnet.org/Bible-Origins/6_The_Apocrypha_The_Septugint/index.htm)
True; while St. Paul writes that "all" are inspired, there is some question of whether "all" should have the same status as canonical. The short answer is that the Septuagint is not really a well-defined collection of books. We should think of the Deuterocanon as of the set common to most Septuagint copies. The Catholic Encyclopedia explains:
there are considerations which bid us hesitate to admit an Apostolic adoption of the Septuagint en bloc. As remarked above, there are cogent reasons for believing that it was not a fixed quantity at the time. The existing oldest representative manuscripts are not entirely identical in the books they contain. Moreover, it should be remembered that at the beginning of our era, and for some time later, complete sets of any such voluminous collection as the Septuagint in manuscript would be extremely rare; the version must have been current in separate books or groups of books, a condition favourable to a certain variability of compass. So neither a fluctuating Septuagint nor an inexplicit New Testament conveys to us the exact extension of the pre-Christian Bible transmitted by the Apostles to the Primitive Church. It is more tenable to conclude to a selective process under the guidance of the Holy Ghost, and a process completed so late in Apostolic times that the New Testament fails to reflect its mature result regarding either the number or note of sanctity of the extra-Palestinian books admitted.