Hello, i have read that especially WRs and RBs have a high drop in their abilities in year 9 and later. Is this the same with LBs and CBs?

Similar or same. TES too at yr 9. Oline and dline is like 12. AT these points there is a severe athletic drop off for that camp and first half a season. A player with 96 speed in his prime but is at yr 12 might still have 69 speed after losing some 20 points by the time year 9 is over.

QBs are yr 12 as well. Kickers may be later. I had a dline drop 20 points speed and 17
acc. at yr 12. It is all tied to the retirement of a player...its when the clock starts for the assigned position

When you bring up the player page, the progress tab will show you a graph of overall rating. On an older player, you can tell where/when the speed dropped. If you mouseover a point on the line, it will tell you the exact sim.