Hi Jorge,
I personally think not having carbon may lead to some issues, particularily if you are using the Probiotic Program. Every system out there that is a bac driven system requires active carbon, even if run passively. The contaminants that can be exposed to our tanks is more than we see, dust, detergents, aerosols, our hands, many different unsuspecting chemicals that can wreak havoc. I would go back online with well rinsed carbon ASAP if it were my tank, assuming a faulty heater could have caused this, active carbon could have absorbed some of the toxins released. GFO is not necessary, unless you have PO4 readings. First things first, water change. Next, get some carbon even if in a sock into your tank, hopefully this will halt any chain events unfolding in the reef. Next, KISS.... Do this until you are certain you see encrusting or tip growth on corals. Alk can change quickly, I should know as I too have had a bout of issues regarding tip burn from alk spike, so go slow, focus on stability, be consistent with feeding. Remember, light changes can cause corals to increase mineral absorption or decrease, based on PAR output, so this will influence change in alk, increases will most certainly irritate corals. I have been testing alk everyday for weeks now, I make adjustments each day, this is my plan until I heal from my alk spike. I suspect I will see gradual increases as the corals heal. Fortunately, I am only dealing with about 6 corals out of 60, so not too concerned. As far as biology, keep to the plan, your tank will bounce back in no time at all