Switched contacts and now very blurry

I was wearing Acuvue 2 and switched to Oasys about 2 months ago. My BC is 8.8 but they only had Oasys in 8.7. I got them anyway. They were fine but I began having trouble after a while (eyes getting irritated and red when I took them out) so switched back to Acuvue 2. Now everything is blurry when I wear Acuvue 2. Why would that occur? Has wearing the wrong BC changed my vision? Do my eyes just need to adjust to the old type? I'm planning on giving contacts a rest for a while and just wearing glasses but am curious why this would happen.