Google "brown jelly infections". If that's it, frag the affected polyps and toss them. Do some large water changes to reduce any elevated DOC. In such a new tank, these kinds of corals should not be added. Far too soon for an unstable tank. Hold off on any further additions for at least another 5 months. Softies should not be added until about the 2-3 month area.
What time of day was the pH tested, was it tested immediately after removing the sample from the tank and was there any chemical additions (buffers) made just prior?
Cheers
Steve