Sounds like your chinchillas are a bit more sensitive to the heat than mine. I'm grateful you were able to get the temperature down. Praise God!
Over time your pets will get used to the higher temps but you will still need to be careful. I should mention that something you can do in an emergency is to put some cold unopened cans of soda in the cage, or half-filled frozen water bottles. (Don't fill a bottle all the way and freeze it or it will split) and top it off with liquid.
In my experience my chinchilla does not like chilled surfaces so you might want to see how that works for yours.
A very common thing to do is use a marble or granite slab. Pet stores often sell these "chin chillers" and put one in the refrigerator and one in the cage and swap them out. Again my chin doesn't like to sit on the chilled surface but it's something you can try. When they are not chilled my chinchilla is attracted them. I also have a big piece of marble from an old dresser.
When using these items please be careful that your pets don't get under them when you are positioning them and get hurt.