I had a bout of that same algae that you have in the first 2 photos...
That stuff was actually kinda interesting, I even left one batch of it growing just to see what it did... :lol:
Its very easy to get rid of since it is a free floating (almost plant like) algae Sabine. You have 2 different algae's going on in your tank... the one I speak of does not "attach" itself in the same way as the hair algae of some sorts you have on the leaves.
I removed all of that stuff by hand very easily...it will very lightly almost glue itself but does not penetrate and damage any leaves,driftwood, or stone.
I first saw it growing in my Riccia bed and at the time I had only had the riccia 2 months, so I thought it was something that riccia does. :roll:
However it had nothing to do with water parameters in my case... it just grew more like a plant . I could pull strands of it right out of the Riccia and some were quite large.
When you remove a piece of that, set it on a dark towel and look closely at it... you will see the tubular body at the thickest points, almost like a stem . The patch I was "growing deliberately" got about 3" around and was really pretty kool till I accidently "pythoned" it out of my tank during a water change... :evil: (wife distracted me... LOL)
Anyways...that stuff can be removed easily...
Now your other algae that is attacking your plants leaves is more serious and indeed does have water quality issues. Also how long are your tank lights on for? ... any windows near this tank? Enough water changes? Best way for now until we get some details is to get as much of it out your tank as you possibly can...clipping leaves, removing any covered rocks etc. and then we will work on the why's...
The leaves that it is attached to will most likely not survive it anyway's so dont be shy when clipping... I made that mistake once and fought a losing battle :cry:
After removing it, do a 25% water change, let the filters run for a few hours and then clean the filters out, this will give you a good jump on it cuz it can spread rapidly.
Dont worry,this too shall pass Sabine
On a side note I hope someone can give a name to the other stuff because I "Googled" my fingers off trying to give it a name !