I don't use tap water. Never said I did.
My current tank is a total ugly, PITA. That's another thread though and I don't want to bring that into this thread. I have a thread all about it already.
For this thread and trying to find the "issue", we can't definitively say it's the RO water being used. We just can't. We have no clue what's in that reading. It could be "stuff" that is totally acceptable and the average reef should be able to handle and even possibly use. It could also be super toxic and killing everything. The latter is extremely unlikely since the store that provides the water isn't killing SPS in 2 days using the same water.
To claim 100% (your words) the OP will see a difference with "better" water is misleading and false hope. COULD it be the problem? Yes. It could also be 99 other things. Things we can't even detect or test for.
The one common theme that stands out is the use of dead rock and a young tank. Do some have success with SPS, dead rock and young tank? Of course. Does that mean that isn't the issue here? No. There are way too many reports of dead rock, a young tank and SPS death that we can't rule that out. No matter how stable everything is, how immacualte the husbandry is or what system (Zeovit in this case) is used.
Sometimes things just don't work in this hobby and it takes a major shake up to fix it. For Paletta's tank it was all new LIVE rock and that's been the case for quite a few people. So we can chase "issues" for months on end and may never fix it. The OP could also spend the couple hundred bucks on all new LR and see if that works. (After the new RO unit is setup of course since that is a much easier fix and will be needed any way.)
As for successful tap water tanks, they're out there if you search. Especially in the cheap (sorry any Utahn reading this) state I live in. Our local board is filled with tap water tanks that do fine. It's also full of unsuccessful tap water tanks. My point is that we can't just claim it is one thing because it doesn't meet the status quo of what this hobby has turned into.
I'm sorry but I'd never used live rock again. Been there done that and it was nothing but a nightmare in one of my LPS tanks. It was fiji LR and I had every bad hitchhiker out there but a great white shark. My best tank I had was a LPS with dry rock, a fuge and T5 lighting. I had to frag weekly to keep things from growing out of the tank.