Help with Fleas

Okay so my friend has one big dog (45lbs), two small dogs (under 5lbs) and three cats. Every animal has a ceresto flea collar on but 3/6 animals have fleas. Have been given flea baths, house has been b**mbed, vacuuming weekly. They basically live in a field. What other things help? It’s not an infestation, the fleas are only on the animals heads which confuses me. Possibly worms too? Don’t tell me cap stars and no judgment, trying to help a friend.