Range issues

I have a Kitchen aid glass top range that on Thanksgiving day decided not to cook to its full potential. Range top works but the oven says it is heated up to a certain temp but will not cook food like it should everything ends up under cooked. Cakes etc. not done through out. where to start? It apears that my oven has a double element at the top and they both glo orange when turned on. what next?

Here are your parts
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=KERC507HBS3

See the attachment for the tech sheet.

When in preheat and bake do the upper and lower elements cycle.
This is the norm as it gives a faster preheat and during bake a more consistent temperature profile in the oven.
Could be that the bake element is bad.

Could be a problem with the oven sensor if the elements do cycle.
Below is a good link, check out 7, 8, 20 and 21.
http://www.applianceaid.com/electric-range-repair-topics.php

May also be a bad oven timer/control board.

You may want to get a oven thermometer so you can check the actual oven temperature. Most units will let you calibrate the oven plus or minus 35 degrees.