definitely try out some new diets! i read somewhere that they could be eating their own poop because their not getting the nutrients they needs, as you said above. so try mixing in new fruits/veggies and make sure you’re giving them a good mix and variety a night. cucumbers isnt enough for them. they need a change up to make sure they’re getting everything they need.
i feed mine lettuce, grape tomatoes, cucumbers, apples, pears, carrots, broccoli, mangos, watermelon, melon, cantaloupe and more.
i know pineapple is a good choice for them as well but mine just do not like pineapple.
here’s a couple links with references I use www.sugar-gliders.com/glidervet-60.htm