

Kitchen sink draining slowly now
I had a slow leak and a plumber came round and identified that the waste basket had corroded away. For some reason that had caused a slow leak somewhere.
He replaced the waste basket, washers, and the conical thing. Sealed with silicone.
The leak did indeed stop.
However, I've a new issue now, where the sink drains extremely slowly.
Given everything (bar the leak) was fine for the last 5 years (normal, fast drainage), is it safe to assume that it's the parts he used in the replacement (waste basket, conical thing, washers and/or silicone sealing)?
He remarked that the pipes set up are slightly anti gravity, but that has always been the case.
Thanks!