It was revealed at the weekend that the Kiribati president Taneti Maamau was not attending the gathering, and his nation had formally withdrawn from the Forum.
Nauru's Lionel Aingimea was also understood to not be attending, ostensibly because of the soaring levels of Covid-19 in his country.
Now, Cook Islands prime minister Mark Brown has also pulled out, and said he wants to focus on the election, which is to be held in three weeks.
And Marshall Islands president David Kabua has said he would have attended the summit, but was not able to because of a legislatively-binding action to terminate the country's membership in the forum.
That legislation had resulted from the five Micronesian leaders threatening to pull out 18 months ago over the failure of their nominee to be given the secretary generalship.
A forum committee announced last month that a remedy had been found for this rift and that it would be voted on at this week's meeting
Kabua announced that the Marshall Islands are no longer members of the forum, and haven't been so since March of this year.
The five Micronesian states which raised concerns at the appointment of Cook Islands politician Henry Puna as secretary general of the Pacific Islands Forum were the Marshalls, Kiribati, Nauru, Palau and the Federated States of Micronesia.