This is a plant of Erwarton showing discolouration of the foliage, caused by lower than average temperatures in the greenhouse. I find that quite a few of the Miniatures are affected by this, the darker leaf with a strong zone like Sussex Gem can go nearly black. This does not bother me as once the weather gets warmer, it will grow out and the plant will be back to normal.
The leaf below shows rust spores, I have been lucky and not seen any for a number of years in my greenhouses. This leaf was on a plant I bought from a nursery, luckily I keep any bought plants seperate for a few weeks. I removed this one leaf and sprayed with Dithane 945, this normally does the trick. By giving plants plenty of space in between them, and opening windows and doors whenever I can helps prevent rust. Also a fan to help circulate air is handy for those days, when the windows and doors cannot be opened.