Fusion,
You might have several things going on here. It sounds kinda crowded in your 25 gallon tank, so chemical warfare between various species is a probability. Do you have a skimmer on this tank? A skimmer or occasionally running carbon can help remove toxins.
IMO, the temperature swings are more important than the absolute temperature. A tank kept at 84-86 degrees will be healthier than one that daily swings from 78-84 degrees. In all tanks, but especially in higher temp tanks, surface agitation of the water is very important to ensure maximum gas exchange.
52 watts of PC lighting is actually pretty week for that size tank ( I have 2 x 96 watts PC over a 40 gallon tank, and 37 watts of PC over a 6 gallon tank, and everything does well), so increasing your lighting might be an issue.
Also, what type of other inhabitants are in this tank? The types of fish or other invertebrates may effect certain corals (again, it sounds like you may have more than one thing going on here).
Finally, I'm a fan of high dKh, but IMO, a 14 is a little high. I prefer to keep mine around 10.
HTH,
Kevin