AFTER waging their own fierce battle of the bulge, JOHN TRAVOLTA and KELLY PRESTON are focusing their attention on their 12-year-old daughter ELLA BLEU, who has put on more than 30 pounds in the last several months.

The 5-foot-3 preteen weighs about 160 pounds, and pals wonder if John is to blame for her eating habits, say sources.

“John has always had a tendency to binge on junk food,” revealed his pal.

“Ella is daddy’s little girl, and maybe he’s passed on some bad eating habits. She loves rich sauces, heavy pastas and an extra dessert or two. She’s a snacker and, like her dad, could live on pizza.”

Meanwhile, John, 58, ap­peared to have slimmed down when he took off for a mid-September Paris vacation fol­lowing an ENQUIRER story on his ever-growing gay scandal. And his 49-year-old wife Kelly has dropped at least 10 pounds in recent weeks.

“Now they’re keeping an eye on Ella and making her the best she can be,” a close pal told The ENQUIRER.

Ella is at an age when girls are especially sensitive about their ap­pearance, and the source says her par­ents don’t want her to start feeling self-conscious.

“To help Ella, they’re bringing healthier food into the house, and they’re eating more salads and lighter dishes, in­cluding broiled fish,” added the source. “The Travoltas are incredibly sensitive to Ella’s feelings and realize a part of her is still griev­ing for her brother Jett (who died suddenly at 16 in 2009). They don’t want her to use food to soothe her­self.

“John and Kelly know how beauti­ful, smart and talented Ella is, and are determined to encourage her to always be healthy and happy.”