Hey Krios,
Falling out of CH remission while on the vitamin D3 regimen can happen to any of us. It happened to me in 2015 due to a pollen allergy and again in 2018 due to a mold spore allergy. We've learned a lot since then.
The winning course of action to get back CH pain free is to start loading vitamin D3 at 50,000 IU/day, ditch the Benadryl (Diphenhydramine HCL) and start taking 3 grams/day Quercetin. Quercetin is an excellent antihistamine and unlike Diphenhydramine, there's no drowsiness or time limit on dosing. Bumping the Turmeric (Curcumin) dose to 3 grams/day also helps. Don't forget the vitamin C. 1g - 2g three times a day really helps.
Stay at this vitamin D3 loading dose for 10 days or until you've experienced a significant reduction in the frequency of your CH for at least 24 hours, whichever occurs first. At that point drop back to a new maintenance dose at least 5,000 IU higher than previous and see your PCP for labs of your serum 25(OH)D3, calcium and PTH. If your serum calcium has remained in its normal reference range and there's no joy as CH beast is still jumping ugly, go back on the loading schedule for another 10 days then shoot me a PM.
Take care and please keep us posted,
V/R, Batch