Maybe that isn't hair algae. Looks too much like slime to me. The light helps corals but is also helps algae. So that is 12+ hours of full daytime light. It could cause algae outbreaks.

it wouldn't hurt to cut back while their is an algae bloom.

I'm wondering about your salt levels. That is the one test you should be able to run at home. Do you have a hydrometer? Too high of a salinity will put most anything in shock.

The petshop told you your water was 1.035 and they didn't tell you it was too high? I'm sure you've heard it before but fish and especially coral need quality water to thrive. Their are several levels that seem to be off and a hydrometer is something that needs to be owned and used almost daily. They are like $5 to $10 and salinity is the first and most important parameter.

the sooner the better....salinity is a key to survival......1.035 is too high. I use the parameters between 1.020-1.025.... mine is a constant 1.024