Are you feeling overwhelmed yet?

The advice is coming in so fast it must be like drinking from a fire hose.
Let's stick with the basics for now.
If your test kit is showing nitrite you tank is not "cycled". Fish excrete nitrogen waste as ammonia (very toxic). Bacteria convert ammonia to nitrite (toxic, but not as bad). Another group of bacteria convert nitrite to nitrate. (Not toxic if the level aren't too high). Once your tank is cycled, meaning you have sufficient bacteria, ammonia and nitrite should read 0. Since your tank is not fully cycled your inhabitants are at risk. Reduce food for now, to lower ammonia coming into the system, and increase water changes to export ammonia and nitrite out of the system. Once nitrite reads 0 you can reduce the frequency of water changes.
Don't over focus on the lights. Again, corals like stability more than anything else. As long as your lights are in the ball park, I would leave them alone. One caveat: make sure they are not too bright. Corals die slowly from insufficient light, but very quickly if they are getting too much light. If you plan to adjust the setting, focus on the blue end of the spectrum and minimize the red end of the spectrum. An over simplification is that corals like blue light and nuisance algae likes red light.
If you corals are looking stressed it is much more likely due to water chemistry than your lights. Your chemistry parameters are pretty far off what is recommended. Another reason for water changes. Part of "chemistry" is water flow. Corals need water flow to move oxygen and chemicals they do need to them and water flow to move waste products away from them. The experts often say "flow is more important than light". Looking at your picture it appears your corals are more the stony type and less the large polyp fleshy type. Short of blowing up a snowstorm, or tearing coral flesh off of the colonies, I would recommend more versus less flow. If you stir up some dust from the sand bed, you should see it moving nicely around the tank confirming good flow.
In summary; for now reduce food and increase water changes. Think stability when it comes to lights. Keep the flow rate up. Don't add ANY more corals until what you have is doing well. I would avoid any more fish until nitrite reads zero and then only consider an herbivore to help control algae.
Or, yes. You asked about green hair algae. Is it good or bad. It is good only in that it is soaking up some of the nitrogen waste from your fish. And, it might be providing some food for your inhabitants. It's BAD in that it is ugly and typically grows out of control. Your tank is entering the "ugly phase". Most of us have gone through it. Hang tough and don't give up. We can help you get past the ugly phase once we get your tank stable and safe for your babies.
Last, but not least, I agree with DonTavo27 ... "get the 4 little ones involved."