Try offering more vegetables than fruit and expand the menu to include a wide variety of fruits and vegetables.
I feed one fruit and one vegetable each night - but different ones each night so my gliders get at least 7 different fruits and 7 different vegetables.
I use primarily use -
mixed vegetables, broccoli, green beans, sugar snap peas, spinach or kale, and okra.
cantaloupe, honeydew melon, watermelon, blueberries, blackberries, papaya and mango