I am having a nightmare with my tank

I am having a nightmare with my tank and wondered if you could all help.

All of a sudden i am getting red hair algae grow all over the place and my
mushroom corals will not open! The African bush coral opens fine but not all
the time. These are my first two corals for some time (since i have moved)
and i cant believe i cant keep these.

At first i thought it was the lights so i replaced the single 250W MH bulb
with a new BLV Nepturion 14K bulb and 2x new 54W T5 Atinic bulbs... if
anything the growth of algae on the front glass and red algae coverage is
worse! The lights are on for 13 hours a day ( from 8am til 9pm).

I have no adverse readings in the tank, Phos is 0 (i have a phosphate
reactor) and nitrate is very low hardly showing any colour using a Salifert
test kit.

What the hell is wrong, is it that i am feeding too much or are the lights
on too long.. has anyone got any ideas.

Some details:

About a week ago i noticed an elevated SG of 1.030 which i have now fixed.
All top up water is RO/DI

The tank is a 60x30x18 inch tank with a 24x18x20 inch sump with a 6 inch DSB
and Calurpa in it and is lit for about 18hrs a day. Skimmer is a Tunze 3140.

Circluation is via twin Tunze 2002 centrifugal pumps, a Tunze 6100 and an
Eheim 1260 return. So im sure thats enough circulation.

I have 1 Purple Tang, a pair of Perculas, a Scarlet Hawkfish, an Orange Spot
Goby and a Green Chromis, two cleaner shrimps and a serpent star. I feed
them 2 chunks of Gamma food a day (Mysis/Squid/Brineshrimp) which i dont
think is excessive nutrients.