I'm starting a new campaign with a few friends. They're all pretty new so we rolled level one characters and it's been going okay, with one minor problem: one character has a +9 to perception and it's ruining many of my traps/secret doors/surprise encounters.
She rolled a Firbolg Rogue with a wisdom of 20 (she rolled an 18 for one of her stats and firebolg gets +2 to wis), and chose to be proficient with perception. Plus, with the rogue's expertise feature, her proficiency bonus is doubled. Thus, we have a perception bonus of 5(wisdom)+4(proficiency)=+9.
First, I'd like to ask if I screwed something up, and, if so, what can I do to fix it? Having stats retroactively changed sucks for everyone.
Second, this poses a minor problem. She almost never fails to detect secret doors, ambushes, and the like. Even a DC20 check she'll get half the time, and these are supposed to be hard. I've planned some pretty interesting ambushes that have gotten foiled. I want my players to do well, but if they constantly notice everything, it seems like it'd be less fun than to occasionally miss things and deal with the consequences.
My questions are: Is this actually a problem or am I overreacting? If so, what can I do to fix this? The only thing that would be really effective would be to start making all the checks DC20, which would discourage other players and seems unrealistic (i.e. is the secret latch on the chest really that hard to find?)