I was attempting to use a common potion on my Sheeta (I turned it to a Sheeta with a Lilac Elixir) and it says it's an invalid combination. This worries me because I was planning on using a glacier potion on her.
I'm a little confused, is it a glitch or something?
Common potions haven't worked since their release. File a ticket and a UA will change the pet/delete the potion.
-- All the other potions work fine, you don't need to worry when you change her Glacier.

you don't need to turn her common before using the potion, just so you know! you could just leave her lilac and when you're ready to use to glacier potion, just use it.