Those are lithops and they are very hard for me to grow. They only need to be watered once a month thoroughly, let the water drain through the pot. Pat the lithops dry of any remaining water. It needs to be in as much light as you can give it. Once a year it sheds its leaves. Don't water it for about 3 months but it still needs to be in the light. Lithops and most indoor cacti have problems with mealy bugs and fungal disease, The top one might have had some water and it looks like surface scarring
I can't believe that only cost you $1.49 mine was only as big as the pebbles and it cost $10.00
Happy gardening in Hawaii. Gardens are where people grow.