First time betta owner, curious about what I can do to improve Luna’s health

I’ve posted about her once before but, she’s a rescue betta, I got her from someone who wasn’t able to take care of her properly but I love her dearly! This has caused a rushed setup to get her in a new tank and rushed research.

I believe I got a lot right since she looks MUCH better than when I first got her, she looked blind in one eye, it was covered in white, but the white stuff went away after a few weeks in the new tank.

• ⁠Tank size: • ⁠Heater and filter? (yes/no): Yes, both. • ⁠Tank temperature: 77~78 degrees Fahrenheit • ⁠Parameters in numbers and how you got them: I need educating on how to take samples, I have a test tube but not sure how to test properly. • ⁠How long have you had the tank? How long have you had your fish?: Tank and fish about 3 months. • ⁠How often are water changes? How much do you take out per change? What is your process?: 25% water change every 2 weeks. • ⁠Any tankmates? If so, please list with how many of each: no tank mates • ⁠What do you feed and how much: pellets, I give her 3 in the morning and 3 at night time. • ⁠Decorations and plants in the tank: mostly live plants, I have 5 in there, only two fakes but they’re soft and not prickly. I have a mini table and a rock fixture. I have pebbles/rocks at the bottom. My goal is to get her a bigger tank soon and use soil in that one. I’ve posted a picture of the tank before, I’ll add prior post here as the setup hasn’t changed: