The first step in this level is to drop some springs (line blasters) down level with the top pet and free it from the cage.
Next, create large groups of blocks (using the paint you have earned to help) in the color that the butterfly requires.
This butterfly will rescue the top pet.
Do the same for the next Pet.
Make use of any balloons that drop and use the paint brush wisely.
Ensure that you have a Pet ready to be saved before you release a butterfly.
The final Pet can either be rescued the same way, with a butterfly, or by shifting the column to it's left so the Pet can drop down.