To get 3 Stars on Level 10-1, you only need the rainbow bubble. If you use the 3 holes in the ceiling Magic potion, you will probably not get the 3 Star score that you so much desire, as it might snitch away the virus bubble that starts right in the middle ceiling row. You need the viruses for wo reasons. 1) You can not burst them and that means that they will fall into the cauldrons as a big cluster. 2) you can shoot rainbow bubbles at the viruses to gain green spiders.
Start the level focusing heavily on the middle part(see attached strategy pic), so that the virus don’t drip TOO much. A little virus is good, as i wrote earlier,, but you are in big trouble if you don’t control the infection.
Here is a 3 Star video where you can see that this Level is clearly tested for 3 Stars without Charms. You might want to read up on howto use the rainbow Bubble to get green Spiders.