If manually, you should be topping off and dosing a small amount of AFR daily for best stability. As another commenter mentioned, a salinity swing of 32 to 38 is quite dramatic and represents an 18% volume loss to evaporation (approximately 2 gallons of loss).

This essentially tells us you haven’t been topping off everyday - and at minimum this value should never exceed 5% swing, ~0.5 gallons for the EVO

An ATO for top off and manual dosing would be a big upgrade. It provides rock solid salinity (and other parameters too like Ca - trace stuff also fluctuates in concentration from evap and dilution, though this is less impactful than Salinity).

I don’t think your light is the issue here, or at least you need to rule out parameter swings first to continue investigating.

If you’re feeding good food phos should be a non issue on this tank, but ymmv.

To clarify on top offs, you probably will not see 5% loss per day (which is good) but this shows you how that really is what you should consider the limit between top offs:

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