Recently completed amateur draft in a league.
Sent a few offers for the top players.
Today - all of a sudden - it appears as if the bottom half of my draft were all sent offers (and signed).
I am positive I did not do this on my own accord.
Anyone heard of this happening?

Did you have your rookie league team full? If you have under 25 (maybe its 20 I forget), than the website automatically signs low-cost draftees and IFAs.

From the FAQ:

If your RL roster is not complete (at least 25 players), the AI will sign enough of your draft prospects to fill out the roster. Before the AI does anything though, you will receive an email a few days before RL is scheduled to begin. This email warns you that RL will be starting soon and you should make sure your roster is complete, otherwise the AI will sign the draft picks.

Yeah I did at the time.
I didn't know it would do it that quick.
Thanks for the info.