one of my young Nepenthes miranda hybrid got the yellow spots on the leaves recently. Other plants next to it is growing normal without yellow spots. I wonder what wrong with this little guy. I grow it outside under double-layer 40% shade cloth in Houston. The medium is LFS + perlite with some living sphagnum as topping. It sits on a shallow tray of water almost all the time.

Any comment is welcome. Thanks,