A few thoughts I can contribute from dealing with Cal and KH lowness on my tank and some of the other things you mentioned:
1. I was dosing B-Ionic 2 part without much success in getting my Cal and KH as high as I'd like (was floating under 400 and 8ish). I started dosing B-Ionic Mag 1x a week for a few weeks and that stabilized it. I'm now dosing the 2 part 2x week (and might go back to every other day), but skip it if I do a water change (which I do about once a week with ~1-2 gallons in a BC14 that holds about 9 gallons of water). The addition of the Mag dosing instantly stabilized my Cal and KH into params that were more in line with what I had hoped for: 440 and 9. If you're worried about dosing Mag, just get a test for it. I test for it, I use the Elos kit and it's a no-brainer.
2. I switched from Instant Ocean Reef Crystals to Brightwell Reef Salt. This seems to be more consistent and stable.
3. I was so concerned with lighting for SPS in my tank (which has a LED retro in it, 42W of CREE LEDs plus 4 accent/moonlights at 1/3 power) that I ended up over-lighting the tank and lost some color on the SPS mounted high in the tank. I started lowering the dimmer by 5% every two weeks and am at 85% now. I've seen great improvement. I'm thinking about going down another 5%. Additionally, I've lengthened my ramp time and lowered full intensity lighting time. I've already seen better color, and yet growth and my little Maxima in the bottom of the tank is doing just fine.
4. You might be over-feeding. I was, again, worried about not having enough light (turns out it was the other way around), and in turn was feeding the corals 2x or 3x per week. I've taken this down to less food and 1x or 2x per week. The theory here, so I'm told, is that the more you feed the less they need to be photosynthetically active (I'm not about to go out on a limb and rep this position as 100% accurate). Whether that's true or not, the practical result in less feeding for my tank has been good for color, but has certainly slowed growth somewhat.
5. The number one SPS growth related thing that I do is the B-Ionic dosing. I have some softies that seem to suck the Cal right out of the water, and when I dose the 2 part 2 or 3x per week, the SPS grow faster.
6. My tank is young, too. I think that's just the nature of the beast with young tanks, and so more testing and constantly adjusting dosing/lighting/feeding is just the way it is. There are a lot of moving parts with a small tank and a new tank, so I'm always reading and asking people about their approach. The number one thing for SPS that I've learned, though is that keeping the Cal, Mag, KH where it needs to be is most important for the health of the coral overall.
Just a few thoughts from an SPS noob. Good luck!