On Sunday it was revealed a Northland woman had contracted Covid-19 before leaving her 14-day spell at the Pullman on January 13.
A child and an adult - who were also staying at the Pullman hotel and left on January 15 - have also tested positive.
Tough new rules for exercise and smoking have been introduced at the Auckland managed isolation facility at the centre of the latest Covid community outbreak.
A returning Kiwi at the five-star Pullman hotel says new measures have been introduced overnight allowing returnees to get out of their rooms for limited times throughout the day.
But everyone wanting to escape their accommodation for some exercise or have a cigarette now must book a time slot.
She also mentioned there had been no communication from management about whether people who had finished their mandatory 14 days could yet leave.
Henderson and Mendez have been dating since last year, and have shared their romance openly on social media - posting cooking demos together, and behind-the-scenes snaps from their dates.
Henderson has also previously received congratulations on his relationship from two former co-stars: Jennifer Garner and Ellen Pompeo.
Garner, who played Henderson's wife in TV movie Miracles from Heaven, commented on one of his photos with Mendez, writing "I'm so happy for you," with love hearts.
Pompeo, who played his love interest on Grey's Anatomy, added in four red love hearts in support too.
In Henderson's latest TV role, in the Netflix romantic soap Virgin River, he plays Jack Sheridan, the love interest of Melinda Monroe, played by Alexandra Breckenridge.
Last month it was confirmed a third season is on the way.
