See this is the trouble with these sites and one thing I'm not a fan of. People are always there to point out something they think is wrong when they don't actually know. I would be worried about your nem but not because of lighting but because of nutrients in the water. It looks unhappy based on the picture but not because of lighting but because of water quality. So I have two points of advice that you can easily do to help solve potential issue. One make sure you do regular water changes and keep you nitrates below 20 which can be difficult in a smaller tank but you can do it! And maybe you already do. 2nd annenomes are sensitive to salinity so if the tank doesn't have an auto top off try and give it a top off daily so that the salinity stays constant and your nem should look fuller. If you ever think there may be something wrong or want to just make sure it's healthy put on a pair of gloves if you want (I don't) and just touch one of the tenticals lightly with your finger and see if its sticky. If its sticky he's ok. But by looking at him he's not ok. One thing that could be making him look tht way is the bubbles. They will stick to it and cause irritation. Bubbles in salt tanks are bad.
Good luck with the tank and as always good luck in the hobby.
Also a note on mandarins because they are my favorite fish and I have trained 3 of them to eat frozen foods. If he has an interest in all with frozen foods start weening him off pods
and on to food slowly slowly slowly and when he actively come up to feed when you feed and stuffs his face you are ready to not buy $$$$ pods
again lol. But if you notice him not eating frozen anymore go get pods
because they will suddenly go on a frozen food hunger strike every now and then it seems.
Sadly I have to agree with mr.x in saying that clown doesn't belong in that tank along with the damsel. Now there is one thing that could change this. If you got your nem healthy an the clown started hosting it you could leave it in then tank because he won't need much room. However I'd ditch the damsel. I was lucky and got a damsel that's very sweet and you may have one to but I can tell you keeping you water quality up with those three fish is going to be a difficult task and will probably require 2 water changes a week.