Bar chewing at night!

[Babble]

Hi all! You've prob seen plenty of posts about this but i really need a lil bit of advice! A few days ago my shyest piggy pair started chewing at the bars during 1am - 9am, I truly believe they are doing it for food (nuggets). They did use to do it but stopped a while back. As of today, they started their early morning rattle at 1-2am, I ignored them putting on my headset + music, even with ignoring them they were on and off the bars to 8am. (Eventually i got up at 9am-ish to feed them their nuggets).
Is there any way to stop them, or kinda show them making a racket wont get them anything?

 

[Ramia]

I leave the room for a half hour and they learn not to do it.