Regarding 1 John 5:7
For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. (1 John 5:7)

Ellen White never once quoted it and a great majority of Bible Commentaries tell us that this verse has no legitimate place in the Scriptures. In the Seventh-day Adventist Bible Commentary, it says,
“The passage as given in the KJV is in no Greek MS earlier than the 15th and the 16th centuries. The disputed words found their way into the KJV by way of the Greek text of Erasmus (see Vol. V, p. 141). It is said that Erasmus offered to include the disputed words in his Greek Testament if he were shown even one Greek MS that contained them. A library in Dublin produced such a MS (known as 34), and Erasmus included the passage in his text. It is now believed that the later editions of the Vulgate acquired the passage by the mistake of a scribe who included an exegetical marginal comment in the Bible text that he was copying. The disputed words have been widely used in support of the doctrine of the Trinity, but, in view of such overwhelming evidence against their authenticity, their support is valueless and should not be used. In spite of their appearance in the Vulgate A Catholic Commentary on Holy Scripture freely admits regarding these words: “It is now generally held that this passage, called the Comma Johanneum, is a gloss that crept into the text of the Old Latin and Vulgate at an early date, but found its way into the Greek text only in the 15th and 16th centuries” (Thomas Nelson and Sons, 1951, p. 1186)

For a comprehensive study on 1 John 5:7 and why its exclusion is justifiable - Click here

It needs to be noted that the pioneers were anti-Trinitarians. They believed in the Almighty One, God the Father, the only begotten Son of God and the Holy Spirit of the Father and the Spirit of Christ as the third Person of the Godhead, called the Holy Spirit. It was in the 1931 Fundamental Beliefs that the word trinity was first used. In 1981 the Trinity beliefs became hardcore as the Father, Son and Holy Spirit were addressed as God the Eternal. This meant that there were three separate and distinct Beings independent of each other, a position no non-Trinitarian could ever take.