To amplify: the court sent or is about to send notices to all the creditors in your original matrix. You'll need to send similar notices to the new creditors. B.R. 1009(a) requires that notice of the amendment be given to the trustee "any to any entity affected thereby", which probably includes all of your original creditors plus anyone who's managed to file an appearance in the case and requested service of all notices and pleadings. Debtor's counsel ordinarily maintains these lists, so it will be your job to do so.
I don't think it's strictly necessary for you to send copies of the amended schedules themselves to the new creditors, by the way. Creditors ordinarily get copies from the court if they're interested. Your notice of the amendment will alert the old creditors that any copy they previously obtained is now stale. At 7 cents a page through PACER, it shouldn't be a big deal.
Get those notices out right away. Creditors are entitled to 20 days notice about the 341 meeting under B.R. 2002(a)(1). If you've already received your copy of the notice from the court, copy it and mail it immediately. Then attach a certificate of service to the amended schedule you file with the court. If you have NOT gotten your copy of the notice, call the clerk's office and see if they have time to include your amended matrix in the mailing they're about to do. Don't expect them to be happy with you.
If, by chance, it's now too close to the 341 meeting, you will ALSO need to call the trustee right away to give him the option of rescheduling the 341 meeting.
