Mushrooms and support minion stacks are all on elevated terrain,
my Steam Guide gives an easier look on their locations:
https://steamcommunity.com/sharedfiles/filedetails/?id=3470044569
Precise directions of towers are also included.
Minion stack 1: 2-3x mage, 1x spider
Minion stack 2: 4-3x mage, 1x spider
Minion stack 3: 1x mage, 1x spider
All three stacks are summoned on top of the torches.
Mushroom on South is on top of the statue
Mushroom on North is near the tip of the spike on that rock
2x huntress guardian pets and 2x monk guardian pets are required during waves.
2x app guardian pets are optional but can provide additional help.
Flash heal to repair auras during waves.
Tested working by several 5k-6k stat players in pub lobbies.