Hi, your ph is low 7.4, this tells me that you have high co2 in the tank (algaes can use co2) try and use kalkwasser to bring the ph up, kalkwasser reacts with co2 helping your tank condition.
your no3 is too low I’d look at dosing neonitro or potassium nitrate. Both of this comes in no3 skipping the ammonia stage that GHA assimilate easier than nitrates.
Having a low no3 will bring you a lot of problems including beneficial bacteria going dormant and dinoflagellates.
once you got the ph and no3 in balance finish the job with cuc.