Yesterday, and only yesterday, both Lightroom and Photoshop were running very slow. Both are the latest versions. And I'm running Mojave 10.14.3 (latest version I think).
Every tool had lag, both in Lightroom and Photoshop. Particularly the Adjustment Brush in Lightroom and the Normal Brush in Photoshop.
It was so bad I considered ending my contract and buying Affinity.....
New day, opened up Photoshop and found that my preferences had been reset, I saw a welcome screen that usually indicates a new version of the Photoshop had been installed, but it was exactly the same version as before.
Actions I had loaded some weeks ago were gone. The same for brushes I had loaded as well. Also, Styles I had created were gone but luckily saved in my CC Library.
More importantly, my performance had improved back to normal.
I did find out later that brush lag with Mojave can be caused by not allowing PS access in Accessibility Settings in Mojave. But, the performance of the brush in PS was fine. But, to be on the safe side I allowed PS access
I have now noticed all of my products have reset preferences and are treating me as a new user or at least someone who has just updated their software