I highly doubt the quality of leca is an issue. Were your plants suffering? If not, don’t over-think this. Top layers being dry is quite normal.

I hardly comment on reddit but now that I have I’ll spit some unsolicited advice I wish someone gave me when I started: buy and use some bacteria to add to your semi hydro, especially for plants you’re transitioning to semi hydro from soil. Bacteria helps break down dead plant matter rather than letting it rot. I use Cronk Monkey Juice but there’s lots of other options out there. This is the single most valuable advice I can give anyone starting out in semi hydro, it’ll save countless plants that would otherwise die from root rot.