I normally start collecting the ingredients after I start a new brew. Not a big problem normally if you checked your inventory, but often the alpha acids of the hops do not match the recipe and you have to recalculate.
I added automatic recalculation to the site and update the recipe to reflect the new hop amounts.

NOTE: If the recipe has been brewed before, the changes are only visible on #brewmates, not on #minibrew.
Let me know how it works out for you.