Beatriz,
Do all the demands appear on the warehouse on the same day? What is the Transportation duration and do you have any GR/GI processing times? Are you using any shipping or receiving calendars?
You can alternatively analyze the situation by starting with a clean slate. Run location heuristics at DC1 and DC2, save the results and see how the distribution demands are spacing out with respect to the demand at the WH. Do you have any other demand at WH other than Forecast?
Regards
AK