All I will say is we put a bit more in the concierge hosts tip envelope than we put for our servers and room hosts, people that did much more for us. If I had my way I would have given less to the concierge hosts and more to the other folks.
I am not going to tip just because they are in the lounge and keep it clean etc, I tip for services provided above and beyond to my family.
DCL covers the work they do, we tip for services provided, which in our case was next to nothing.
Go with your gut on tipping, you may find that server tip money is too much for each, or too little. Just go with your gut and don’t feel guilty regardless of how much you tip them
Edit - Have to say that the fact that DCL doesn't give any guidelines on this made the tipping stressful at the end, because while you don't want to be insulting, you also don't want to tip more than you felt they earned. They should to set the floor for the tip and then say tip more depending on the level of service.