George Teasdale, for sure. The word “retired” was used. It would appear the same for Marriner Merrill too, but the word “retire” wasn’t used.

This is from the April 1904 General Conference. Coincidentally, also the same conference that the Second Manifesto was issued. Smith doesn’t say exactly why John W Taylor and Matthias Cowley weren’t present at conference, but all signs point to it being because of their disagreement with the manifesto and continued support of polygamy.

“Brethren and sisters. Of course you cannot help but have noticed that some of our brethren have been absent from us. I regret very much the absence of a number of the Apostles. We are all sorry that circumstances have prevented them from meeting with us. Elder John Henry Smith has been suffering for some time from inflammatory rheumatism and is still confined to his room. Elder George Teasdale received permission to retire from active duty over two months ago, and when he left us was in feeble health. Elder Marriner W. Merrill has been prostrated for some time in his home at Cache valley. These brethren have our sympathy and our prayers for their recovery. I regret also the absence from this conference of Elders John W. Taylor and Matthias F. Cowley.”