Verify that your temp is really set to 200Deg C.
Cheap thermometers are just that....cheap.....and inaccurate.
Get a Digi K sensor type and use that to set your oven.
very slight wipe off ( can just see a tiny weenie slight colour on the cloth) is OK.
Is is better to bake too long, than too short. Long will darken the colour.
Short will cause failure