Catalpa is an early summer bloomer.  Its flowers open after all the foliage on the tree fully emerges in the last few weeks of May or the first few weeks of June.  These developing buds are the new leaves emerging.  The small amount of tip dieback on these branches is not something of concern.  Often, this happens as a result of cold winter temperatures.  The tree will recover just fine.

Newly planted trees (within the last 3 or so years) are more prone to winter dieback as they are often under more stress, which can occasionally lead to a little dieback over winter, even in a winter-hardy species.  As the tree becomes more established, this type of winter damage will be less likely.  From what I can see in the photos, the little tip dieback you have is of no concern.

Further questions can be directed to your local county Extension office. This local resource is very helpful since they are familiar with trends and issues in your part of the state. Click on this link to get connected directly with a staff person in your county Extension office and ask your gardening question. https://yardandgarden.extension.iastate.edu/ask-gardening-question.