Dying Plant, HELP!

 HELP, one of my babies is dying!

This beautiful dying plant is a Gold Dust Plant. It was doing very well until a month ago, it became an ant farm. This is when the baby started not to do well. My friend and I took it outside, for it to get more sun and fresh air. Of course the week, we take this baby outside, the weather decides to get cold and rain...

 →It's a fighter

Here are a few more babies that are alright.

 Gold Dust Croton & I can not remember the other plant

Cactus and mini Pony Palm 

Me with one of the babies.

The star plant, Dragon Tree.

Plant Resources:
1. the spruce
2. Guide To Houseplants