What's up with these Urchins

[Dr RBG]

These two were put in the DT a few days ago. I noticed them "linked up" today on the glass. While watching them a shower of small differently colored balls came from one of them. Any ideas?

 

[cristata.reef]

Urchin poop. If they were mating you'd see some white liquids coming out and some real foggy water around them