Yup... actual numbers for the water chemistry tests will help us help you. Specifically... salinity, pH, alkalinity, calcium, nitrates, ammonia, and nitrites. Phosphate, if possible.
For a year old tank, I'd expect to see a LOT more coralline algae present - even with low lighting. I suspect something is up with your cal/alk
levels. Did you start to add the calcium before or after the corals starting retracting?
Also... what kind of fish do you have in there, and when did you add it?
[Edit: Also... things could have been good for a while, even with inadequate flow or lighting, because it can take a while before a coral shows the effects of either of the two. They can "survive" quite a while in inadequate conditions before finally just giving up and running out of extra energy to stay alive.]