My 5 month old puppy keeps trying to eat other dogs feces

Recently my 5 month old puppy has been trying to eat my other dogs(2 yr old) feces. The first time it happened was about 2 weeks ago. Our puppy sleeps in his kennel but our dog doesnt and during the night she happened to have an accident which is rare. Anyways I went to let our puppy out of the kennel and he ran over to where she had had an accident, which I hadn't noticed yet, and proceeded to swallow a piece before I could stop him. After that I've started to notice him trying to do the same thing again. Like I said he didn't used to do this it's a recent thing that has been going on. I'm just wondering if there could be something wrong with him or if this is a common issue?