They have done a fair few miles anyhow so you'll notice a nice improvement with new discs and pads. Do a fluid change whilst you are at it as that makes quite a difference at this mileage and no point having new discs and pads without doing the fluid. Potholes and bumps will not make any difference to the discs either as they are all unsprung weight. Something else has happened there, maybe they have got very hot due to heavy use with worn discs and pads perhaps??
Never heard of Delboy before I watched that video , so I can't comment , but what he is doing there makes perfectly good sense to me ..... .... just my two chetrums worth
Where to you start the list is endless... Headstock bearings Copper slip Machining Bodgit and scarper bike builds Just have a search around YouTube to see correction videos from people who know what they’re doing