There’s a section of our yard that stays green

You’re not being paranoid, that’s a classic early indicator that effluent is reaching the surface layer sooner than it should. No smell and no ponding means you’re catching it early, which is the good version of this news. Worth having someone assess the field before it progresses, since early intervention is dramatically cheaper than a replacement. We had Rock Solid look at ours; their Septic Services includes drainfield work, and in our case it was resolved without a full rebuild. In the meantime keep vehicles off that area and redirect any downspouts that drain toward it. Getting it looked at in dry weather also gives a clearer picture than after a week of rain.