Are these symptoms of being poisoned?

My two teenage sons and I have for the past few days been experiencing some strange symptoms. I was wondering if they could be symptoms of poisonsing of some sort. We have all had headaches, stomachs cramping, blurred vision, muscle tightness, and diarrhea. One has also had chest pain, and both boys have complained of sore throats.I have been very tired, but thought maybe that was just stress...although I'm not so sure now. We are living with someone who is diagnosed as bi polar with violent tendencies and very much does not like us. She is on multiple medications, and has in the past said she has put visine in enemies drinks. She has complete access to our refrigerated food and when I make coffee my coffee pot is also accessible. Is there something she could have put in our food or drinks? The symptoms started about 4 days ago, after a particularly nasty argument.