Your lighting is good, your flow is possibly sufficient, depends on how you have it arranged.
More water flow would be good. Flow is more important than lighting for corals.
I would be concerned that maybe you have some alleopathy (chemical warfare) going on, and with very few water changes plus no carbon, any new corals will have a hard time adapting.
Rowaphos can be hard on sps if you're using too much. How much are you using, and have you always used it?
The pictures might help a bit more.
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Mitch
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