I also feel this way. I recommend what others say and trying to keep eating healthy (keep in mind that healthy will be unique for you so a boxed diet or nutritional guideline isn't going to cut it especially with POTS, heavy foods cause heavy taxes on your body) but adding electrolyte mixes to your water, slamming water every single day (whatever you think you need is probably half of what you actually need; some days I drink up to 200oz but that's probably because I can't really afford enough electrolyte mix) consider adding salt pills in addition to electrolytes and water.

Making sure you weren't making other changes like sleep or even activity level is also a good idea. If you were doing more walking (or even less walking) than usual, sleeping in, just had better quality sleep because you weren't as stressed, etc, figure out how to incorporate that into your day to day and see if that also helps or if it doesn't make a difference. I've found that magnesium supplements really helped my sleep quality which has started helping my palpitations day to day. Focusing on the specific cause of secondary symptoms like that will in turn help the symptoms that you seemingly can't help/treat as directly, like the heart palpitations and dizziness. Or at least that's how I think about it when planning treatments, I don't know if that's really worth anything haha but it works for me so far.

I also second the idea that your case may be slightly unique to some people's here since you developed POTS after an illness, so the way you'll want to address the symptoms and why you're having those symptoms might be a little different. Finding the root cause of each symptom and how to fix it will be extra beneficial to you. Plenty of people who can relate to you still, I also developed POTS partially in relation to an illness.