Both ways! I killed a couple plants because I put sulfur in them. I checked the pH and it was near 3.0. If you use Holly-tone, or Ammonium sulfate you’re adding acidity to the mix. If pH starts to become low, I start watering with tap water which is about 8.0 and has some carbonates. I usually use rainwater. Peat and pine have a pH of 5.0 so you don’t need to adjust pH, it’s at a good point as is. Their are fertilizers that don’t lower pH but are for acid loving plants such as Miracle Grow, for acid loving plants. It uses Urea which is only slightly acidic. Urea nitrogen is fine for blueberries.
I make a mix of pine bark fines, peat moss, and perlite sized diatomaceous earth. In a ratio of 3-2-1/3. DE is slightly basic, but you’re not using much. It is not necessary but in root pouches they dry quickly and this helps maintain moisture and drainage too. Many studies show it is an excellent soil amendment. Holds 120% of it’s weight in water, contains silicon a necessary micro nutrient used in cell walls. It holds more water than calcined clay, pumice or lava rock. I get it at O’Reily’s auto parts as Optisorb floor dry. 100% DE, also Napa makes various different products but one Napa floor dry is 100% DE.
In a commercial setting you may be able to buy bulk, and even horticultural DE Except for one company DE for plants is only sold wholesale. I would buy a bag and have a few test plants, to see if they do better or not before I would add it to all. I use it for all plants myself in containers.
The reason for my mix is at one time I saw a study on growing blueberries and they grow fine in straight pine or straight peat, but the most growth was seen in a mix of 3-2 pine to peat. So that is what i use.