If they are over-exposed, then you'd want to decrease the development time. Which is actually a method many of us use regularly.
Originally Posted by handle2001
If your temp was lower than 20C/68F, then you'd normally need more time to get the same result as at 20C/68F. Chemicals work faster at higher temps. On the Ilford site, there's a chart for temperature compensation. I do remember that if the time for 20C/68F is 9 minutes, then the time for 18C is around 11:15 minutes.
Personally, the edges look fine to me, so the development was likely alright. Are you also sure you mixed the developer as per the instructions? If the developer was too strong, then less time and a lower temp would all balance out as well.
I agree that the squiggles look like dust on the film at the time of exposure (they look like cotton to me, though I can't guarantee it).