Rust on comfrey leaves

Ok so one side of the comfrey plant has got slight rust on the underneath of some leaves, i gather its best to pull off and dispose of said leaves.

Can i use these in comfrey tea, compost pile or are they not usuable and need to be burnt.

Stopping it happening is it just a case of thinning it out and letting the air get to it.

No need to yank all those leaves off then  Lol