Never been to Lemp specifically but I've done a fair bit of location work in old mansions and cellars over the years and there's something about spaces where genuine trauma happened that just sits differently to your average "haunted" tourist trap. The air feels thicker somehow, like the place is holding its breath.
The Lemp family history is genuinely grim - multiple suicides in that building, that's not nothing. That kind of concentrated grief and desperation has to leave something behind, whether you believe in residual hauntings or something more active.
What exactly did you feel down there? Was it more of a pressure/dread thing or did you get any specific impressions? I'm always more interested in the basement accounts from that place than the dining room stuff which feels a bit performed for the restaurant crowd tbh.