An almost 50% water change with chloramine water would do it. The fact that they all rtn at the same time made me think it was the water or some kind of contaminate. You did mention that you buy your water from a LFS but the corals look ok. If you test their water you will probably find ammonia a biproduct of chloramine. The difference between your tank and theirs is their water changes are less frequent and much less volume. I have had an issue with chloramines myself and I am sorry your tank is crashing definitely hard to readI did a water change after the sump install. Total of 15 gallons. I usually do a 10 gal water change weekly to keep nutrients in somewhat check. I took a ICP sample and got it sent out. Just waiting for the results. It wiped out all my sps. The few lps i have are fine.