Im a bit confused when you say your doing a low tech tank, but your dosing EI and have high light etc. (2w/g is still highish light)

Im not sure about the melting plants, but the algae probs are more than likely due to the unstable conditions and high light compared to zero CO2. 2 w/g with no CO2 is quite alot in my eyes.

If your doing EI, does this mean your doing water changes as well?

If you are, then this isnt going to help you either, as all youll be doing, is replacing the Co2 deficient water, with CO2 enriched water, this is going to give you a huge seesaw effect in your CO2 levels, something which your plants are going to find horribly hard to cope with, and the algae very easy. For plants to get used to low CO2, its far better not to do water changes very frequently, some people dont do them at all in fact.

Remember, light drives Co2 takeup, Co2 takeup drives nutrient takeup. What your doing is limiting your tank via Co2, you have the light, the nutrients, but no way for them to take it up. Algae needs far far less Co2 to grow. Also, algae will target slow growing, stunted plants.. you hardly ever see algae growing on a healthy plant.

I would try to decide whether you want to do a techy tank, or a non techy tank, and then stick to one or the other.. at the moment, your trying to do something in the middle, which aint gunna work.

Instablity is one of the worst causes of algae problems, as happens alot with DIY Co2, I spent a good 10 months banging my head against a wall with DIY Co2, before I found this place and people told me what was going wrong. Instability.

Im not experienced in low tech tanks, but Im sure someone can suggest a schedule for you to follow that will get you back on track. But its going to be based around minimal ferts, minimal light, minimal water changes. Good luck with it