Pictures?

This sound strange considering there would be different types of caulk. It is possible to have a bad batch. I had this happen for some siding and the manufacture had me pull the batch numbers on the tubes and sent me a check, but this shouldn't be the case for you. What is the humidity around?

In my experience, it takes about a year for everything to "settle" as Johnson Brothers said ^^^^. That means you'll experience caulk separating during that time. It's happened to us in every single house we've owned that we built or remodeled. It's not a huge deal, just a bit of an eyesore. Our agreement with our builder was that he'd come back after 6 months to recaulk and he did. It's fine now except in a few places. Still not that big of a deal since I'm pretty handy with a caulk gun.

Thank you. I think the caulk is shrinking more than cracking, so settling may be the issue. I'm not sure what our humidity is, but I assume since it's winter and we're running our furnace, it's pretty dry. I will get some hygrometers and find out. I will also speak to our tradesmen about coming back in the summer to touch up or re-caulk as needed.

We have humidifiers on our hvac units and still couldnt get our humidity above 38%. this while it was very cold outside and in the midwest. so we bought a portable humidfr and are keeping it now about 48-50%. our wood trim behaves better at the higher humidity level. healthier bodies with humidty a little higher too.

cheap hygrometer from amazon works great.