Is my Yveltal EX Standard Legal?

I paid £30 for 2 x Full Art Yveltal Ex (XY series 144/146) and I have the Black Star Promo version too which I know IS standard legal for the new rotation in September.

Question is does this make the full art versions legal too?

Yes. Any card that has had a true reprint (the name and all relevant text on the card is the same) in a standard-legal set is considered Standard. This usually us used to apply to Trainers, but it applies to Pokémon too. Generations in particular was largely a reprint set, meaning it kept many early XY Pokémon Standard and will continue to do so through this season. A more common example in tournaments of a Pokémon applying this rule is baby Yveltal, also from XY, which is Standard because it was directly reprinted in Steam Siege.

Thank you :)

So glad that i can use it post September