Here is my setup of bettas in vase's. The lighting is Marineland single bright LED. Works well enough to work as a cover so they dont jump out while providing a nice color. Has blue LED as well that look nice as well. They are located in my media room which has a very stable room temperature so never fluctuates more than 3 degrees any given day. Water changes of 80% done daily with aged water. Clean vases for algae or any other buildup on glass weekly where 100% of water is changed.
Cories need to be kept in groups of 3 or more and they need a minimum of a 10 gallon tank. IT is not fair for it to be in that vase.
Is the vase heated? Betta's must have a water temp of 78-84 to be comfortable.
Please consider putting them in a proper tank with a heater and more cories.
I appreciate your input and your concern, Cory's don't NEED to be in groups of three or more. And 10 gallons is a recommendation, we've all felt the need to preach before including myself. That being said, the Cory isn't in the vase for good, it's a holding tank until my friends tank (15g, don't worry ) is ready. Which will have THREE OTHER CORYS, PRAISE JESUS. And the temperature is more than adequate, right by a windowsill with direct sunlight. I've been doing this for about 10 years now, and take every consideration before setting something up. I hope I set your mind at ease.