pH isn't really as important as it was thought to be not very long ago. What is important is the dissolved salts in the water such as those responsible for hardness (Ca2+, Mg2+, CO3 2+).
That being said, your water is on the hard side (although about 1/3 the hardness of my tap water). So you could use peat to soften your water but there are 2 problems I have found with my experiences. (note: i havent used peat granules, but only gardening peat moss inside pantyhose etc.)
1. This is the most important problem - the water change dilemma - what do you do when you need to change the water on your peat-softened tank? Adding tap water will increase the alkalinity and hardness dramatically only to slowly be brought back down again by the peat. This would likely be more detrimental to your fish than just leaving them in your tap water. The second option is to run your tap water through a pail filled with peat (hole drilled in the bottom) and have than dripping into another pail. I have done this when I was a kid and its a pretty big PITA. But if money is an issue, its cheaper than RODI or distilled water.
2. Your water will be tea coloured. Some people like it, but most dont. Just tell people its a black water biotope
IMHO, I would just stick with what you have got. A lot of people have it a lot worse off than you. I would just take it easy and just not get super soft water species.