Question
What causes the outer leaves of African violets to become bronze in
colour (or yellow in light green foliage plants)? The plants are not
thriving and the outer leaves are unsightly. They are potted and
fertilised using the same ingredients as in previous years when no
problems occurred.
The problem also occurs with other Gesneriads.

Answer
The plants should be in a pot that is 1/3 the size of the plant.  That is the first thing I check.  Browing and yellowing can be due to sitting in wet soil.

The soil mixture should be very light.  If you want to use commercial mix lighten it up with some perlite so that the roots can breathe.

Next the fertlizer you use should not have any urea in it.  This will burn and eventually kill your plant.  Make sure and follow the package directions on any fertlizer you use.  If you fertlize everytime you water cut the fertlizer down to 1/4 of what the package says.  You can easily burn a plant with too much fertlizer.  Also, using fish emulsion in your fertlizing program is a great benefit to the plants.  This gives them much needed nitrogen and helps to guard against yellowing.

The yellowing is usually due to a lack of proper nitrogen in their diet.

Here are a few sites you might find usefull.http://www.avsa.org/
http://www.avsa.org/AvsaLinks.asp

Happy Growing
Kristina