The large chamber was just a DIY extension with chopsticks in each corner and some clingfilm to cover the sides. I've literally just remade it for the yellow oyster flush that's now going.
I had a hygrometer delivered today but it doesn't really fit in the chamber(s) sadly. I need to build bigger ones really.
That's a good point about the seasonality of the mushrooms, something I'll definitely take into account going forward!
Re your comment about the mycelium overlay, are you referring to pic IMG_1245.jpg where it has protruding nodules?
I don't have a probe thermometer but I think I will invest in one now

It drops temp at night so hopefully that will have an impact and I'll use the ice pack trick tomorrow to keep the temp down during the day and see what happens.