Red dwarfs could take their first billion years just to calm down enough to allow any nearby planets to be habitable. And the “habitable zone” around such stars is very close indeed. All seven of the Earth-size planets crowd so close to their star that they complete a single orbit -- their “year” -- in a matter of days, 1.5 days for the nearest planet and 20 days for the farthest.
That kind of proximity means the planets are probably tidally locked, with one face always turned to the star, the same way our moon presents only one face to Earth. And while red dwarfs are “cool” compared to our sun, they would loom large in the sky of a close, tidally locked planet, perhaps baking the sunward face. The far side, meanwhile, could be trapped in an eternal, frozen night.
The right kind of atmosphere could mitigate such effects, transporting heat to the planet’s far side and helping to moderate the climate overall.