You've been hit by a Mega Event that restricts all ship speeds to a maximum of 5 for the duration of the game. There aren't a lot of things you can do about it, but it only takes effect on the turn after a ship is built, so your first turn with each ship will be full moves. You may want to consider using all-engine designs in order to move your ships the most distance possible in that turn, and then upgrade them into what you really want them to be-although this will be more expensive.
In general, you probably want to turn Mega Events off, as this isn't really avoidable otherwise.
