When it's cold plants' water requirements decrease (think about transpiration). A decrease in growth goes along with this. There's a good chance your Oyamas are over supplying your plants under these conditions. This can promote root rot and other bacterial and fungal diseases. If I were you, first I'd find a warmer, yet well lit location to get them out of the cold. Creating a lighter mix might not be so bad either and help them recover. Whatever you, do act quickly. Rotting leaves are an indication of a serious problem. Remove dead or dying tissue, repot, and keep warm.

Good luck,
R

Unless your perlite has a lot of small particles creating a "clay" like substance, it should have worked well in the oyama pot. It will "wick" the water up into the soil mix. If all you had was the soil in the bottom of the oyama pot, the soil would stay way too wet. Any time you think the soil mix is staying too wet, you should repot, adding more perlite into the mix...also I think 1/3 vermiculite is a bit too much too...there should be some in there, but probably not quite 1/3. Also keeping a little less water in the reserve might be helpful until your plant recovers. I use the regular sized perlite myself. The cold will slow down the blooming...plants do need a rest now and then too. I'm zone 7b and I grow plants in my windows, your area should be warmer than mine?...but all houses are different.

Tish is correct - you need to add at least 1/3 of perlite to your mix - better medium perlite - or if you have the reguar one - small to dust - sieve it - or rinse it in a colander- to remove the dust part. Replace the perlite in a bottom of your Oyamas to a coarser one, use lighter mix- and when you refill water - better water more often but with small amounts.

I.

I know this is an old post, but I thought I would update. I bought some 'professional' AV mix on Amazon and my AVs are much better. They were just too wet in the Home Depot type soil. It wasn't the Oyama pots. I also found horticultural grade perlite that is much more coarse than the stuff regularly available, which helps a lot. I also am not in a rush to fill the pots with water. I let them dry out completely now and just try to refill before they start to wilt.

Thanks for the update, it is timely, the pots sound like a good idea when getting ready for travel and vacations and need to leave plants alone for a few days.
Joanne