I Donate Plasma Twice A Week. A Few Months Ago

I donate plasma twice a week. A few months ago after I donated I was at a movie theater and got sick. I couldn't walk and my center of balance was off for two days. Since then I have continuously donated plasma. Today I was feeling great/normal and then all of a sudden my vision blurred and I was concious while my legs gave way and I realized I couldn't stand anymore. Then I went out. My friend who was there believes it was a seizure. It was a little under a minute and coming out of it was not fun. I don't think this is normal, but is there a correlation with plasma donations?