Thanks for the advice, It's not clear in the image, but there was some mold on the bottom of the large shroom, if you look closely at it in the bottom left you can see what looks like holes, it was slightly green there.
I've thrown the cake, and I've ordered another kit, it will be another few weeks before I'm ready to harvest again though what's the risk with the mold on the shroom?
The weight of the big shrooms dried is about 6g, it was sliced and I've broken it testing it's dryness, so not sure exactly which bits are the big one anymore.
Mines running on an OG pi for I have no idea how many years, I've never changed the SD card ( hopefully haven't jinxed myself π€π )