so im doing the part with the potions, and i accidentally used a mort myre fungus when i was filling my druid poich, and somehow didnt pick up one of the ingredients for the guthix balance potion. what do i do?

If you're unable to get the ingredients again down there, you'll have to get them elsewhere and bring them with you.

I did the exact same. Just go out and grab the stuff you screwed up, just as Monkeyguy said. Pain in the [wagon], but recoverable.