the shop *should* be work fine to progress through upgrades, Seems like you ran into the same problem a few people have been having where the water and air shards are a little too similar looking when they are shrunk down to the icon size so you think you have the right resources for an upgrade but you do not. Possibly will have to do some re spriting in the future or swap the order of the dragons to put some separations between water and air to make the differences in the sprites more clear. thanks for playing :)