I work with CU's and come across different things I've found they include in on their sites which cause delayed loading times and issues with memory. Some of which are easy fixes some which aren't. Some are coding some are not. I'd question the development company and ask them about which development mode they are using. There are a few:
- Portal Engine
- Portal + ASPX
If they are using straight ASPX or MVC, there is a huge opportunity for errors and issues because they are essentially recreating the wheel and writing all custom code for things which Kentico has already created in Portal mode.
Feel free to reach out to me directly if you need further assistance.