Just about 2 months ago, we renovated our kitchen below our bathroom. We used to opportunity to replace the old galvanized drain pipes and old barrel p trap for our bathtub with pvc. This was done by the plumber sub my contractor uses. Everything went pretty smoothly except for starting a few weeks after I now notice a smell from our shower overflow. The overflow and drain are pvc replaced 12 years ago. I attached some pictures of the pipe layout. We have one big old main vent line. The tub connects to the sink which now connects to the toilet. I’ve cleaned the drains with bleach and it helps but only temporarily. I’m not sure if it’s sewer gas but when I get up on the overflow , it’s got a musty earthy smell. I called my plumber and they didn’t smell anything they said and recommended cleaning my drain. It’s all new drain lines i don’t get it. I’m concerned my p trap is being siphoned. I don’t even know how we’d correct that. Sorry this is a bit of a ramble but any help is appreciated!