When cory cats lose their barbels it's usually due to a really high amount of nitrates in the water or sharp substrate. Since you have playsand I would lean towards your water parameters being the culprit. How often do you perform water changes? If you increase your frequency it might help. Not sure if the CAE could be a culprit since I've never kept one, but I heard they can be problematic once they stop eating algae.
I'm having a similar problem with my ghost cats. I received the same suggestions re: reducing nitrates (difficult because my tap water has pretty high nitrates to start with) and increasing the flow in the tank since ghost/glass cats prefer a strong current.