processing – Why did my developing tank almost burst open when using citric acid as a stop bath after developing with caffenol delta recipe?

I developed with Caffenol for the first time tonight, using the Delta Standard recipe I found online. Developing went fine. I had a bit of trouble loading the film, but I got it. The problem came when I had to use the stop bath. I pour the Caffenol down the drain, then poured in the tank what I normally use as a stop bath, which is citric acid (I’ve always developed with D-76 before, and had no problems). I started to agitate and noticed the tank got stuffed, as if it were filling up with air. I agitated once more and it almost exploded. Luckily, I was agitating in the bathroom and didn’t mess anything up with this solution. But I got light leaks on my negative, and I’m thinking it had something to do with this. So I was wondering what might have caused that?