Yes, you can buy pH up, or you can use baking soda... But if you have soft water (sodium is used to soften it), using baking soda (sodium bicarbonate) might be ill-advised, as it might give your plants too much sodium.

Even with a pH kit that only goes to 6, you can estimate a lower pH. If you're using a Wadley Jr. kit, a pale yellow with no hint of green or orange is about 5.8. (5.5-5.9 is optimal to avoid any nute lock-out.)

I'd recommend getting a wider-range pH kit & some pH down. You could also use store-bought water, but I think the former is a better longterm solution, as long as your plants seem happy in your water.

Green thumb to ya!