Front derailleur chain rub

Thanks guys. Even on the middle chainring? I was under the impression cross chaining only applies to the inner and outer chainring on a tripple FD
No, the available chain ring/sprocket combinations are dependent on two things: chainline and chainrub.

Chainline refers to having such extreme combinations (big/big or small/small) that the chain runs at an angle that causes excessive wear of itself and the cassette and chain ring.

The wider the cassette the greater the problem: a 1x5 set-up will happily run all options.

Chainrub is more apparent when using the smaller rings, because the bigger rings overlap them: you might get rub in the two highest gears and the small ring, but none from the lowest and the big ring (but chainline could then be the issue).

With a triple, I would set it up so that the available gears are evenly in the centre, ie lose one gear from either end.