One thing we as baseball fans should always always always be mindful of is that power is streaky. If a guy hits 26 homeruns in a year, it's not going to be 1 a week every week. It's going to be a couple weeks with 3-5 each and a lot more weeks with zero. In fact some months are only going to be 0 or 1.
With Happ, the contact and exit velo numbers are down a little bit, while the groundball numbers are up a medium amount. I tend to think his issues are injury, and that if Bellinger and Seiya hadn't already been hurt he'd have started a short IL trip around the Marlins series. But also I feel like the underlying issues are minor enough that you could still handwave it away as early season weirdness. I definitely don't see anything in his profile that rises to the level of alarming. So this article is well written and well measured but the handwringing on Twitter about Hapo is wildly out of scale with the extent of the actual problem.