Surely you can see that you are merely demonstrating that my assertion is correct. You are referencing material outside the Bible to claim such and such about the Bible. Whether that is unbiblical, extra-biblical or something else is beside the point, because it certainly isn't "using only the Bible" or demonstrating that "the Bible is enough." Seeing that nowhere in the scripture contained within the Bible as we have it today is there a decree to "close up shop," per se, and bind up the volume, the early fathers were either acting on their own initiative, acting on guidance by the Holy Spirit, acting under some directive from someone or whatever, but they certainly weren't acting on anything in scripture contained within the Bible as we have it today.
Perhaps I wasn't clear. The Bible is considered “God breathed”, divinely inspired created by the Holy Spirit through the men of God who lived the moment. It is from the Bible, and the Bible only, we derived our doctrines and theologies. No extra writings are used. Consequently, we do not create or base doctrine or theology on any part of the early church fathers’ writings. These writings, like other non-church sources of the time, are viewed for historical purposes only.
The church fathers had their share of disagreements (the Septuagint is just one) and issues of their own. But what these writings contain is information on the thoughts, life, and doctrine of the early church and serves as a guide or commentary in understanding the scriptures. They were not perfect men and they differed in interpretations on some issues. But they were solidly united in the core beliefs from which many of the creed came about.
As far as whether it was "scriptural” to “close the books” I’m not sure. However, given there was much heretical writings flooding the market (and since I might add) the church fathers were united in this to preserve the purity of the original text.
Did they make the right decision in closing the book? Given these were the church leaders who sacrifice all that they had and, in some cases, gave up their lives for the gospel and our Lord Jesus, I’d say that qualifies for a BIG Holy Spirit inspired effort.