This is a very frustrating situation i come across it myself on a local 18 acre park lake that i fish, The thing is with weed carp love it, its full of natural food bloodworm and crawlers so they naturaly visit these areas for food on a regular basis. Also weed retains heat, so at night when the surrounding water tempreture is dropping at night, fish are therefore drawn to these warmer areas, it in effect acts like a radiator, try it for yourself cast into it at night and bring some in feel how warm you will be surprised.
Now it all depends on the extent of the weed growth, if the weed is