From the Writings and Utterances of `Abdu’l-Baha:
Buddha also established a new religion, and Confucius renewed morals and ancient virtues, but their institutions have been entirely destroyed. The beliefs and rites of the Buddhists and Confucianists have not continued in accordance with their fundamental teachings. The founder of Buddhism was a wonderful soul. He established the Oneness of God, but later the original principles of His doctrines gradually disappeared, and ignorant customs and ceremonials arose and increased until they finally ended in the worship of statues and images.
(`Abdu’l-Baha: Some Answered Questions, p. 165)

The Message of Krishna is the message of love. All God’s prophets have brought the message of love.
(`Abdu’l-Baha: Paris Talks, p. 35)

Blessed souls whether Moses, Jesus, Zoroaster, Krishna, Buddha, Confucius, or Muhammad were the cause of the illumination of the world of humanity.
(`Abdu’l-Baha: Japan Will Turn Ablaze, p. 45)

From Letters Written on Behalf of Shoghi Effendi:
Regarding Lao-Tse: the Baha’is do not consider him a prophet, or even a secondary prophet or messenger, unlike Buddha or Zoroaster, both of Whom were divinely appointed and fully independent Manifestations of God.
(Shoghi Effendi: Buddha, Krishna, Zoroaster, p. 20)

The nine religions to which you have referred include both the Babi and the Baha’i Dispensations, Baha’u’llah being the ninth Prophet in the series. The other Prophets included are Zoroaster, Krishna, Moses, the Christ, Muhammad, Buddha, the Prophet of the Sabaeans Whose name is unrecorded, the Bab and Baha’u’llah…. Buddha appeared in the Adamic cycle.
(Shoghi Effendi: Buddha, Krishna, Zoroaster, p. 20)

Regarding your questions: the only reason there is not more mention of the Asiatic Prophets is because Their names seem to be lost in the mists of ancient history. Buddha is mentioned, and Zoroaster, in our Scriptures – both non-Jewish Prophets or non-Semitic Prophets. We are taught there always have been Manifestations of God, but we do not have any record of Their names.
(Shoghi Effendi: Buddha, Krishna, Zoroaster, p. 22)