It is possible that the judge can revoke your participation in the diversion program (usually reserved for first time offenders) and put you back into the regular docket for adjudication of the first charge. Your problem then positions you as a multiple offender . . . forget breaks or leniency due to the subsequent charges (same judge and jurisdiction?). You were given an opportunity to escape the first case without a record, now you must face the consequences of your behavior.
I think it is the judges' decision to decide whether you're guilty or not if you get additional charges while on pretrial diversion program. However, depending on the state you are in your Pre-trial diversion case is subject to re-institution of prosecution for a violation of your probation. Inform your pretrial diversion coordinator for any new charges.