These spots are the start of a fungal attack, no doubt due to the rainy and warm conditions you have been experiencing.
Keeping them as dry as possible and only watering when the soil is quite dry will be beneficial.
Spraying them with a milk and water spray could also help, perhaps every other day until there are no more new spots forming.
One part full cream milk to ten parts plain water is the magic formula.
Hope this helps, Organoman.