Will leaking struts cause tire cupping?

All four tires have the cupping problem. Toyota dealership cannot get the two tires that are now on the rear to balance because of the low tread. Do not know if these tires were on the front and they just rotated them to the back or what. Have had these tires rotated as required. 20 point safety inspection performed at each service never indicated any problem. In fact was marked as ok. But on the same date was told needed new struts and tires. Now the Toyota dealership is saying there is only mild cupping on the tires. I cannot figure out why they cannot get two of the tires balanced.

Sounds like if your services were all performed by them and you have the '20 point' inspections by them , they would offer a better explanation , at least. tires don't just get bad after 1 service , not all 4 , at least. Have them show you one of the tires they can't balance when it is on the balancer and see if the rim is bent or if the tire has a broken cord (high spot/out-of-round). The tread life warranty is exactly that , tread life , not wear pattern problems , that may have other causes.