Plz check the coke quality.I hope coke should show some more VCM and ash. Probably this is becz of the improper flashing of the increased material in the coke drum.
Consider coke drum as a flashing vessel which should have some design parameter.
Increased in feed rate to that of same vessle will generate less flash (With maintening same delta pressure i.e.feed coke drum inlet to that of the coke drum).
I hope this is the reason why your coke % has been increased.