Rescue organisations normally know best, since they do handle a lot of cases like these on a daily basis. <1 month is really young, poor thing. Since the, can’t eat real food yet, some milk and a cozy blanket will do good. Or wven one of those hoodies with big front pockets. Definitely keep the fur tidy, that is usually the best indication (though I am not even sure on this low are to be honest). Thank you for helping it out. At this age it very much is helpless, on its own yet. The 6 months old is probably fine, as long as it’s fur is shimmering. Maybe put out some wet food with stuff helping with worms for now.