SUBSIM Radio Room Forums - Don't touch my preys!

I m doing my first campagn as a type IX kaleun (used to be a type VII fanatic). Thirst patrol, end of november 1939.
It was a real bad weather patrol. I went north by Scapa Flow in heavy rain and wind. Actualy, the uboat is hard to manoeuvre, we were going up and down a lot. Patroled some day west of Ireland, sunk some ship in this heavy weather at blank point range (300-400 meters). Then I head toward the irish channel, to see if I can find some juicy preys... and here came a convoy on my hydrophone. Looks like 2 warship and 9 to 10 merchants. Convoy was moving 4-5 knots and with the visibility of 400 meters best, I decide to simply move in front of him, placing myself in the middle of his trajectory and submerge. With the heavy weather and in 1939 I was confident about the inneficiency of the escort. By that time they were 15 to 20 miles away but I got them clearly on hydrophone at 25 meters depth. So I sat and waited. And when they were closing at maybe 5 miles, they started to sink :o . Just like that... before being under 1 miles, 5 of them went down. I moved to 10 meters and raised the periscope... they passed all around me without spoting me. Shot 3 of the last merchant myself, the last one was a neutral. But who sunk the other one!
With 5 torpedoes left I decide to head home, but by passing between scotland and the Hebrides Island. Usualy we can take some merchant by that way. Here I went.
Spoted 2 merchants and a warship on hydrophone and follow them for a while... the merchants went down again!
Is a really bad weather is enough to sunk so many ship or do you think they were some other kaleun stealing my preys?