Phil your setup looks very fine!
Lower pH is just a sign of softer, more lightly buffered water, with lower total dissolved solids. The pH follows along naturally from the reduced carbonates.
This is only important if your Discus start to pair up. Then you'll have other problems! Like what to do with the Raphael cats and the rest of the Discus...
Later, for raising fry, less stringent water conditions are fine again. It's just for spawning and egg hatching that extremely soft water (bringing low pH values) is recommended.
You might consider passing some water through a funnel of peat for reduced calcium and magnesium. Peat water has tannins that are beneficial.
Or just relax and enjoy.