I think you're watering too much. They like to be on the dry side.
Anise Hyssop (Agastache Poquito™ Butter Yellow)
Water Preferences: Mesic
Agastaches are drought tolerant plants. Once they get established, they can go without being watered, as you would do with your other flowers. I'd think after being in your container for two months, that it would be established.
From High Country Gardens:
Scroll down to where you see:
The Secret to Cultivating Agastache
The important thing to remember about successfully growing the Hummingbirds Mints is "tough love."
As a general rule, these plants like to grow in hot, dry conditions once established.
As for their soil, the "leaner" (less fertile) and more well drained, the better. Stay away from rich loams and heavy clay.
Fertilize organically with a little quality compost and Yum Yum Mix in the fall. Chemical fertilizers will push these plants too much and weaken their tolerance to cold.
Leave the stems standing over the winter months to increase cold hardiness. Cut back hard in mid-spring.
Mulching is only necessary in arid climates. Use crushed gravel, pine needles or crushed nut shells at a depth of 1 to 2 inches.
Agastache will act like annuals when grown in rich, fertile soils with too much water and fertilizer. They'll grow and flower lushly but are most likely to perish over the winter.
Scroll down to read.....
Tips for growing Agastache
Agastache are sun loving plants with aromatic foliage and flowers. They bloom from mid-summer into early fall and are resistant to rabbits and deer.
Agastache need lean, well-drained soils, prefer gravel mulches, and appreciate deep but infrequent watering after their second growing season
Provide a fast draining soil that's naturally low in fertility, Don't plant into clay soils.
Plant in full hot sun.
Just a few handfuls of compost in the planting hole is enough. Don't plant into a rich, highly amended soil..
Fertilize the Agastache just once in fall with Yum Yum Mix and Planters II.
New transplants need regular irrigation their first growing season to establish themselves. Watering can be reduced greatly during the second growing season when the plants have matured.
To improve winter-hardiness, and encourage re-seeding, leave the stems intact over the winter. In mid-spring, remove old stems just above the new foliage, about 4 or 5 inches above ground level.
If your conditions don't lend themselves to growing Agastache in your garden, they do well planted in containers.
(another link with info about agastaches)