I set my tank up in July 2017, after tearing it down because of a whole bunch of nasty crap...it was an ongoing cycle. Hair, Cyano, Dino's. I'd get the hair done, then cyano appears...get that done, and then Dino's appeared. It was just ugly. Long story short, I battled this for 6-9 months, and got so frustrated, I actually listed my tank for sale. I drained it, removed the sand, and my god, the water was the dirtiest brown color you could possibly imagine. I bleached and acid bathed my pukani rock, let it sit in RODI for a few weeks and replaced into the tank. This time, I went barebottom...this was in july 2017.
Fast forward to now, I have 1 SPS coral...I had a bunch that was doing well, until I screwed up. I had an algae issue, and it's slowly dissipating (brown slimy algae, not dino's). My parameters as of last weekend (I need to test tonight): 7.7 dKH, 8ppm Nitrates, 0.08 PO4, 420 Calcium, and Magnesium as of 2 weeks ago was 1340. My tank is powered by a 6x80W T5 sitting 12" over my water.
Everyone says, it takes about a year, 18 months for a tank to settle in and find itself. I thought that was hogwash, but I think there's something to that. If your SPS do not make it, I would get your fish stocking finished, let your dry rock mature, and tank find itself. Then push into corals. For a hardy sps coral, I highly recommend the Cliffs Acropora from
@BoomCorals. Like I said, I nuked my tank with an additive, but this coral not only survived it, but is growing, and colorful. That, to me would be a good coral to test your tank readiness. Just give it ~300 PAR, good flow, and just let it be, you will be surprised. My frag broke off the frag plug, so for grins and chuckles, I left the plug in the tank, and glued the broken frag to a rock. The frag is encrusted on the rock, and growing. The plug encrusted over the broken part, and encrusted on the rock, and has about 7 buds shooting vertical. It's a bright neon green flesh (Supposedly purple but I've never seen the purple...possibly when it gets to a colony).
PS: I agree with you on Pukani rock. If I had to do it over, I would get Marco rocks, or the Caribsea Life Rock Shapes.
If you ever want to chat PM me, and we can commiserate together. I have been there where you are (and I guess I'm still there in some respects).