Why starbase in not connected to the Trade Network?
Solution 1:
When you claim systems with trade hubs at the end of a war, which it looks like these were, the game does not automatically connect them to your trade network. It's up to you to connect them manually. (If you can; in some cases you might end up with odd borders where systems are isolated from your empire and can't be linked.)
As for the other two systems, my initial guess would be that the game doesn't bother to notify you if no trade is actually being collected by those starbases.