iserith
Magic Wordsmith
I have the opposite problem in the game I DM. In a party of six 4th level characters the highest passive perception is 12. Three PC's have Perception proficiency paired with a wisdom score of 10. One PC has a wisdom of 14 but isn't proficient in Perception. As a group they are much better at Arcana/History/Investigation/Religion skills. They're always pushing me to use Investigation to find traps and secret doors and I'm always pushing back that they have to notice something before they can investigate it. Perception lets you walk around with a broad awareness until something unusual grabs your attention. Investigation is putting your focus on a single thing and giving it all your attention. Using investigation to find traps and secret doors would require a focused examination of every surface: good lighting, brushing off dust, poking and probing, listening, moving slowly, etc. Certainly possible, but time consuming.
If I was in a party like this, I'd suggest we put one person in front to stay alert to dangers and one person behind or next to him or her who works together on the same task. That means there's a passive Perception of 17 detecting hidden monsters and traps as the PCs move through the dungeon. (The person doing the work together task is automatically surprised if lurking monsters attack, but at least the party has a better chance of blundering into a trap.) Every player then listens very carefully to the DM for any description that might telegraph a trap.
When they stop moving around to explore an area, same deal, more or less - each person searching for hidden objects gets someone to work together with them on the task. Any Wisdom (Perception) check would thus be at advantage. Once a trap or secret door is found, now we can deduce how it works based on the clues we just found, which may be resolved with an Intelligence (Investigation) check.
Short of spending resources to boost the result of the checks, this is about the best they can do with what they have I think. They're just better at deducing the workings of a trap or secret door than finding them!