Hair damage

My hair has always been long, dark, thick and full. Since I started living in the Philippines, it's always brassy from the sun and the sea (understandable, and though annoying, fixable with a salon color every few months), but the real problem is how thin it's gotten, the lack of volume, and how sooo dead the ends always are. It feels like someone else's hair now.

I knew being in Asia would eventually change my hair. When I first started backpacking I washed it rarely (usually once a week), and as stupid as it sounds, I used bottled water to keep it as safe as possible from the notorious hard water here. But once I settled down here, I couldn't keep that up, especially since I'm in the water most days and wash my hair way more often now.

I know it can be a mix of a lot of things: heat, sun, diet changes, hard water, etc. But I'd just like to know if anyone has tried something that made a noticeable difference. I'm not expecting an overnight transformation. I just don't want to damage it further, and I'd love to see it get thicker again.

I use a good shampoo and conditioner (sulfate-free) plus argan oil. I try to rinse out saltwater with fresh water as soon as possible, and I never sleep with salt in my hair or go to bed with wet hair. I only use cold water (that's all there is, no shower head, just a tabo, a water dipper). I condition it often, and I never put direct heat on it.

Open to any suggestions at all. Products, diet, supplements, anything. Please please please 🙏🏽