Kribs can be aggressive. My brother lost his betta to one. Cichlids generally have their swiming level from mid to lower. Cories swim at the lower.
I have heard of Rams poking eyes out of cories. Rams are not as aggressive as kribs. From my experience with kribs, they are too aggressive for the most part for the community tank. So I stuck one with the mbunas but they are not able to stand up mbunas.
You have three kribs. If two are a pair and had babies, then they get very aggressive with any fish that goes near the babies.