Give tank BIG clean out turkey blaster on all plants and substrate get as much detritus out as possible.
Clean filter out to remove detritus and maximise output.
Clean all hoses/pipes.
Check CO2 pH profile.
Trim plants where flow is being restricted.
Remove/trim affected plants/leaves if bad
Spot dose LC
Increase tank turnover!
If you’re using tap water try and do water changes before or after the photo period. Tap water is rammed with Co2 as I’m sure you’re aware and fluctuates levels in the tank benefiting both staghorn or BBA before it will benefit your plants. Algae adapts and takes advantage of changes in the environment more rapidly than plants.
Recently been playing around with two tanks suffering similar algae issues (staghorn and BBA) on slow growers. Beyond the regular weekly maintenance all I did was change a basket of media every two days or so until all media was replenished. Algae died back. There’s several potential explanations to this, non of them provable though, just speculation, so will leave it out instead of generalising to your specific circumstances. Important to resolve the source(s) of the issue.
If you have SAE they’ll eat it as it fades. If not then dosing glut or spot dosing will kill it off then cherries and Amano’s will eat it as a food source if you stop feeding your tank (and presuming you have shrimp). If going the glut route I personally dose after the photo period during lights out and double dose 2% glut so 4ml per 100 litres of tank water per day for 10 days or until you get your result.
I'm been doing some testing with the staghorn algae
I got 5 plastic cups each with 200ml of Aquarium water (EI ferts)
Each of these I placed a small sample of staghorn algae and a sample of infected plant.
1 - control (just aquarium water)
very little change as expected.
2- high light (20w led 10cm away)
Staghorn has tripled in size.
3- 0.5ml of hydrogen peroxide added (6%)
Staghorn and leaf dead and white
4 - 0.5ml of glut (excel strength)
Staghorn dead- leaf yellowed but might recover
5- 5 days total darkness
Very little change, leaf not looking the best.
Only real surprise how a 5 day blackout made very little difference.
I want to try a 5 minute dip in a 1/3 glut 2/3 water followed by returning to normal aquarium water. Possibly try similar with peroxide.
Ps there appears to be less in my tank, I still have a infected Crinum calamistratum and some on balansae, as both are very slow growing I'm thinking about pulling them up and repeating a 5 minute dip. I'm going to try with a syringe full of glut but I'm not convinced.
I've also cleaned out my filter and doing 2 x 70% water changes a week.