Here is what is written in the British Admiralty War Diary, available on fold3 (for paying members...)
extract of 13.09.1940:
British Air Operations
Owing to unfavourable weather part of the programme for night operations was cancelled. The following attacks were, however, successfully carried out: on petrol stores at Emden, seaplane base at Nordeney, vessels at Delfzijl, Flusing docks where it is believed an ammunition dump was hit. Flak ships in the North Sea were attacked but clouds prevented observation of results.
3 out of 13 Blenheims today attacked Calais harbour and a concentration of barges at Ijsselmond, results not being observed; and a convoy of 6 or 7 vessels believed to be tankers off Zeebrugge, one ship of which was hit. The remaining 10 A/C abandoned the task on account of weather.
At 1621 A/C attacked 6 merchant vessels each towing barges, off Boulogne, one bomb bursting in the centre of a group of vessels. A Blenheim attacked a supply ship and a convoy of 15 to 20 tugs, each towing two or three barges, near Boulogne harbour at 1650, scoring two hits on barges.
Source:
http://www.fold3.com/image/302053821/