Good on you for going back to the grower feed. It takes like 7-30 days for dietary changes to show up in the flock. If it's the heat, hopefully that will let up soon, too. Of course, if your ladies were headed into a molt, it'll be 2-ish months before you see eggs.
I don't think you see weird eggshells if they're low on protein/amino acids, but production can go down, eggs might be smaller, and yolks and whites can be more watery.
In our limited experience, temporary stressors like changing coops, injury, or losing a flock member cause a lower egg count for at least a few days. Since you mentioned the skunk, predator pressure can also reduce laying. Doesn't sound like that's what you're up against, but we love our trail cameras for making sure nobody's harassing the coops.
Oh, and there are studies about the bioavailability of calcium carbonate vs. oyster shell vs. eggshell vs. clamshell, etc., and whether the size of the particles makes a difference, but nothing seems definitive? The key appears to be making sure your hens like the size/shape of the calcium so they actually eat it, and that they all know where the calcium is and can access it without being bullied.
Good luck on getting that W. Let us know when you see eggs again!