8 months of SSRI's, suddenly feeling off

I started on Lexapro initially, and though it helped my anxiety a lot, I still felt slightly depressed (which isn't something I struggled with before the episode which made start an SSRI), so I switched to Celexa and have been feeling great since 2 months in on it. No more overwhelming anxiety or low moods. Anyhow, I randomly got hit with a wave of anxiety while I was out to lunch with family and though it wasn't intense and I was able to ground myself, I've been feeling off for the last couple of days. Low level anxiety and low mood. I fear it may spiral into something more intense. I'm hoping it just passes. Anyone have any similar experiences on the SSRI that has worked for you?