Sorry for your loss...
With two deaths in the span of two days, I don't think much would have been possible on your part to save these guys anyway. How did the water change go, anything significant on the remaining Chromis?
The only thing I can think of here is possibley Uronema
but it should not have developed so quickly nor caused the deaths in such a short time frame. I'm not sure if it's too late for the remaining fish but I would suggest treating with a series of formalin dips. It will cure the problem if Uronema marina
but you must be sure the fish has no lesions present. If any redness is present, it will not tolerate the formalin with skin damage so you may have to opt for a FW
dip and Methylene blue. Furacyn has also been noted in helping with Uronema if the fish is in the early stages of infestation. Use at a one time dose of 30 mg
for 5 days.