Q.asters
I bought a medium white aster and potted it up. The day after, the blooms were all wilting and going brown. Can you help? I fed the aster and changed the soil to see if there were any weevils.

Make sure that you used a good quality potting soil and a pot with adequate drainage holes.
Keep the soil moist but never soggy.
I would move the pant to a shady location to help reduce the transplnat stress.
Here is a link to refresh on the care requirements of Asters.
https://www.gardeningknowhow.com/ornamental/flowers/asters/growing-asters.htm