I give the tank 6ml of TNC complete each week
, which is about right, weekly dose should be fine , however dosing 1ml x6 days a week would be my preference - little and often
3ml of easycarbo liquid carbon fertilizer once a week (should I be doing this more often??)
Once a week could be causing/compounding the problem, as when you dose it there will be more carbon available, plants start to adjust to slightly higher level of CO2 then non for week. Using liquid Carbon (LC) technically turns the tank into a high tech tank, high tech tanks need better flow rates than low low tanks, low tech tanks have less issues with CO2, so not dosing the LC may be a better long term option for your plants. Lots of folk dose LC to combat/control algae which it does to some extent, however LC is mainly a nutrient which helps the plants grow. LC is best dosed just before lights on, it is broken down by the light but dosing it just before lights on means it will be present in the water for the plants to uptake and use it.
Focusing on algae is always an issue long term, focusing on healthy plants is always the best long term plan, as if you plants are healthy and growing they will out compete the aglae.
Your plant biomass is a little on the low side also, so adding a few cheap floating plants will increase the plant biomass and also reduce the light getting to the lower plants which in turn reduces thats plants CO2 demand. When the lower plants fill in slowly the floating plants can be removed.
2 hours in the morning and then 6 hours in the eevening
Never keen on as split photo period as it is done purely for our viewing pleasure, it is more of an issue in CO2 injected tanks than non injected tanks, however whilst you have the issue I would advise just one photo period say 5-6 hrs at first. Once the holly leaves issue is resolved you could try a short viewing in the morning for your viewing pleasure and keep a close eye on holly leaves returning.
The water surface doesn't seem to be moving much, if you filter came with a 'jet' nozzle I would attach it so it creates more surface movement as this will increase the CO2 uptake of the tank, if no 'jet' nozzle increasing the height of the output of the filer (if you can) will have the same effect.
Have patience with the plants, not every plant you put in your tank will thrive or may not be suitable for various reasons,
@hogan53 has just posted he doesnt recognise the plant and he is pretty 'hot' at his plants, you may have a plant that doesn't grow under water, Local Fish Shops (LFS) will sell you anything and often the salesperson isn't very knowledgeable. Most folks use a 2-3 trys with a plant then if it still fails time to find another.
On the whole a nice start all the same