I think this is normal as hub scores are always fluctuating. The scores of my own hubs are also always changing. Sometimes they increase, sometimes they decrease. If you look at the list of all your hubs in "my account", you'll see that the list won't always be in the same order because the hub scores keep changing.
Generally, if you just published a hub, the score will be low and then it will slowly increase after some time. Once it has increased, it can still decrease although just by a few points.
In my case, what I found was, if I first create a new hub, the score will be really low. If I finish making the hub and then publish it right away, the score will still be low. But if I take a few more days or so to finish the hub and then publish it then, the score will be a bit higher.
To find out more about hub scores, you can check out the learning center guide about it. Here's the link: https://hubpageshelp.com/features/Learning-Center-...