Often an ‘old’ leaf will turn yellow and become ‘blotchy’ before dropping off, however, when this happens to ‘new’ leaf it is a good indicator that the plant is under stress. This could be due to many factors, over/under watering, too cold/too hot and may or may not have been caused whilst the plant was in your possession (sometimes it depends on delivery and storage at the point of sale).

If the plant is over-watered remove from the container if possible and place on absorbent material e.g. newspaper or absorbent paper kitchen towel. If you cannot remove the plant(s), place absorbent material on top of the compost (soil) and push this in slightly so that some of the moisture is removed by capillary action. In both instances replace the absorbent material when moisture has been fully absorbed.

The plant(s) if removed from the container should be replaced after a couple of hours and the process can be repeated daily until you are satisfied that most of the water has been removed.

Although many growers recommend that you should water thoroughly and then leave to dry out many amateur growers don’t seem to know when to water and this can cause them a problem. My advice is little and often, my plants sometimes get watered up to three times a day in mid summer and I can assure you we HARDLY EVER get really high temperatures here in the North of the Uk.

The problem you have though doesn’t appear to be any pest or disease, unless you can see anything on the leaf?

Have a look at the site below as this will give you an indication of any cause associated with pest or disease.

http://www.btinternet.com/~micka.wffps/leaf1.html

I hope this helps,

Tight….