To answer your question yes. Anything less than 100% transparent limits the light penetrating into your tank. The loss may be negligible though, or it may be significant. You'd have to have one of those spectrum testers to find out for sure.
They do look sort of funny with the legs on the wrong way, like a bow-legged lighting system or something, lol.
Overall I think your rockwork looks really nice: there are plenty of places for your fish to swim around/through and I think they'll really like that.