You probably both know how to trigger and upset one another, and probably intentionally do perhaps often.
This allegedly is his child as well. Presumably he loves her, cares, and is active in her life. He gets school alerts.
You know things will be worse between you two if you don't inform him.
Just inform him. This is about your shared child, not about the grudges and animosity that one or both of you have against the other.
If things were reversed, you'd want to know.
Also, it is important to inform him, in case it returns and perhaps gets worse during his time with her, which may require a hospital visit and questions answered.
Both of you participated in the demise of your former relationship, and probably refer to the other as abusive and controlling...which both of you may have been.
From this point on it should only be about your daughter. Not any desires to hurt him by withholding important information from him.
Perhaps if you weren't an a hole and controlling too, maybe he wouldn't be.
This is perhaps you trying to be controlling and being an a hole .. perhaps you find his freak outs amusing to a degree and want to rile him up.