Test one ingredient at a time
Start with the fire active, then test a single mushroom color before mixing. If you add multiple ingredients too quickly, it becomes hard to tell which one caused the visible response. Red appears to produce the strongest response in community notes, while green is a calmer baseline.
For marshmallows, think of distance rather than time first. A marshmallow held too far away will not toast, while one pushed into the flame burns. The sweet spot is near the flame edge for several steady seconds.