A number of synos love plants, feather fins included. (Probably not enough to swap tanks to eat them). But in this case if I were the op I would rule them out, as they would have eaten what look like shoots of vallis or similar rather than swords.
As for the swords. They really need a clay type pre substrate to do well, and if they are grown or of water, which most are, then you can expect to lose some of the stronger looking outer leaves whilst the roots take hold. Swords take most of their nutrients through the root system so you want good strong roots and fertiliser in the substrate.