OK,
this doesn't sound too bad, after all! As the corals are new and seem to be responding to the tank in a positice way; i.e. poly extension, I would say you are in good condition. The corals will need time to adjust to the water and repair themselves. I would think 4-6 weeks as a reasonable amount of time to see clear change.
The pH is a bit high, as is the dKH (alk), therefore I would not add any more carbonates to the system until they drop a bit. The actual values are less critical than the overall balance of the Ca, Mg, carbonate ions. (aim for NSW values) When these are out of balance, then the corals find it difficult to grow. Normally they tend to remain in balance, but CO2, coming from a kalkreaktor can drop the pH while increasing the alk. A reason to be careful with reaktors an monitor their effects. I use one and find it the best method to maintain my system. It may need additional supplements in the future, as it will drop the pH, if I turn it up too high.
As to the PO4, I think you are fine, but would recommend investing in a better test kit. PO4 turned out to be more important than I expected and being able to monitor it on a fine scale is a very advantageous thing. The ROWA kit is kinda expensive (â"šÂ¬50 in Germany), but I found it worth the expense.
One additional item. I have been using Sponge Power from the Zeovit system and it seems to really help corals to grow and develope. I would recommend trying it out. You use it drop-wise, so do not OD !
Now the key is a bit of patience. Stay in touch.