Two explosive fireballs, dodge and drop... and then?

[Onkl]

Hi guys

I'm very sorry to ask this question as I am sure it has already been answered but my search-fu is weak and I did not find an answer to the question I have.

Let's assume there is a battle going on, on one side there are two shamen, on the other there are 2 warriors, running towards the shamen.

Both of the shamen load up and fire an explosive fireball right between the two warriors on the ground. There is no cover what so ever.

After the first Fireball hits, both warriors would probably dodge and drop, but what will they do after the second fireball hits? I thought you always had the chance to an active defense as long as you are concious and see the attack coming. But on B414 it says that you can try a dodge and drop... and not a word about a "normal" dodge.
So would they just roll at -3 (for lying on the ground - plus any additional applicable modifiers) against dodge?
Or would they not have any defense against the second explosive fireball/grenade/generic explosion?

Thanks!

Onkl