From a Protestant perspective why didn't the Apostles address the problem of deutrocanonical books?

At the time of apostles, there was no problem of extra books or Tradition as on par with God-breathed scripture. No problem, so of course no clarification. Everyone at the time, unlike today, knew the difference between God-breathed and man's tradition or Tradition.

It is a well-spread myth that the earliest Septuagint contained as equivalent to God-breathed Scripture the books of apocrypha. From the article

"Strong evidence exists that the Septuagint was the canon in place in first century Palestine. "Authors Archer and Chirichigno list 340 places where the New Testament cites the Septuagint but only 33 places where it cites from the Masoretic Text rather than the Septuagint.""

Philo, Josephus, and Christ, if you can believe it, all recognize and define only the true Old Testament as books written during the valid prophetic times. Even 1 Macc will affirm that it is not scripture because during that silent period it was written when there wasn't a valid prophet!

The idea, like the Godhead, of a Tri-part OT is called Tanakh. These are the Law, Prophets, Psalms. It does not include the deuterocanon.

"The deuterocanonical books (from the Greek meaning "belonging to the second canon") are the books and passages of the Christian Old Testament that are not part of the Hebrew Bible."

We find this three-part Canon in at least three sources. Christ (via Luke), Josephus, and Philo of Alexandria. (emphasis mine)

From Eusebius regarding Josephus' comments on the Hebrew Canon, which again the article references.

1. “We [the Jews] have not, therefore, a multitude of books disagreeing and conflicting with one another; but we have only twenty-two, which contain the record of all time and are justly held to be divine.
2. Of these, five are by Moses, and contain the laws and the tradition respecting the origin of man, and continue the history down to his own death. This period embraces nearly three thousand years.
3. From the death of Moses to the death of Artaxerxes, who succeeded Xerxes as king of Persia, the prophets that followed Moses wrote the history of their own times in thirteen books. The other four books contain hymns to God, and precepts for the regulation of the life of men.
4. From the time of Artaxerxes to our own day all the events have been recorded, but the accounts are not worthy of the same confidence that we repose in those which preceded them, because there has not been during this time an exact succession of prophets.
5. How much we are attached to our own writings is shown plainly by our treatment of them. For although so great a period has already passed by, no one has ventured either to add to or to take from them, but it is inbred in all Jews from their very birth to regard them as the teachings of God, and to abide by them, and, if necessary, cheerfully to die for them.”

Philo of Alexandria mentions the same three categories of Scripture as Luke records Christ saying, the Law, Prophets, Psalms.

"but studying in that place the laws and the sacred oracles of God enunciated by the holy prophets, and hymns, and psalms, and all kinds of other things by reason of which knowledge and piety are increased and brought to perfection."

And finally here is Christ's tri-fold determination of scripture.

Luke 24:44-45 He] said to them, “This is what I told you while I was still with you: Everything must be fulfilled that is written about me in the Law of Moses, the Prophets and the Psalms.” Then he opened their minds so they could understand the Scriptures.

There is Christ defining what OT Scripture is. And it doesn't include things written after Artaxerxes, Malachi times to the fulfillment of prophecy when He walked the earth.

So, the reason the apostles didn't address man's traditions as Scripture is because they knew the difference. Oddly enough, the only ones who do want to include extra books as authoritative are those who are otherwise willing to raise their own men's opinions to the level of God-breathed Scripture in their own denominations. Aside from that, neither we or the Apostles have any problem with knowing what is and what isn't God-breathed.