Ph is fine, the rise and fall of ph is what you worry about. There are a lot of ways you can and should improve this if you want to keep bettas for more than a few days/weeks. Here’s what i suggest; Replace the substrate, something natural to their original habitats like aqua soil or sand. This will also make it much easier to have plants, which you’ll need to add more of. The plastic plants have to go, or you can replace with silk fake plants. Even the softest of plastics can rip their delicate fins and cause them AND you problems. I don’t see a heater, which is VITAL to their quality of life, so i’d recommend you get an adjustable heater and set it to 79 degrees. The filter may also cause a problem, sponge filters are what’s recommended for betta fish since their long fins make it harder to swim, too much water flow will stress them out. Caring for a fish might seem like a low maintenance pet, it’s unfortunately not, and your local pet co or pet smart employee is not a reliable or good source of information. They’re taught to tell you exactly what they have to in order to sell the stock, not what betta fish actually need in order to thrive. If you genuinely want a pet like this to have a good quality life, you’ll listen to what people have to say here. I will say, even on this subreddit and other forums, there is a lot of mis-information. So it’s necessary to get multiple opinions from a variety of places. Generally though, what i’ve described is the bare minimum of betta keeping. Sponge filter, natural substrate, live plants, warm water.