Phaedrus was a Scholarch of the Garden, a successor in a long line of leaders of the school of Epicurus. Philodemus was also a devoted member of the school, having studied under the Scholarch Zeno of Sidon.
Lucretius is probably the outlier here--a Roman among Greeks, as it were. He held orthodox beliefs about the gods, and was not an atheist, but he was more critical of cultural religious devotions than Epicurus was.