[Ellie May]

This isn't something that should be treated at home unless you are doing it under the supervision of a vet in my opinion. Green teeth and red gums most likely means infection. Infection means at any time their heart, liver and kidneys could weaken because of it. They may be in pain. They could start losing teeth.

Petzlife works for some people but for some it doesn't.
The alcohol so close to the top of the ingredient list is questionable.

The teeth do need to be brushed.
I even floss Ellie sometimes.

If they are as bad as what you're describing, I'd go to the vet.
I waited and didn't want to deal with Ellie's mouth and now she is out 9 adult teeth that had to be pulled and a couple that fell out...

I know anesthesia is scary though.
How much do they weigh?

Scaling at home may be okay but you won't be getting all of the plaque and they may look clean which can be dangerous because there is still hidden bacteria/plaque.