Planted Tank - Help!

[thomtom]

OK, I am after a bit more advice as I am confused by all the conflicting information online. I apologize in advance if this gets a bit wordy and I tell you stuff about the tank that you dont need to know but I want to solve this once and for all.
 
I have had my tank planted for around 6 months now and everything is growing upwards as I would like but I am seeing some issues on the leaves of my plants, this is an ongoing issue that is really starting to bug me.
 
Fist of all a brief explanation of my tank:
 
100L: 80cm x 30cm x 40cm
Lighting:2x24W T5 bulbs currently on for 5 hours a day but the tank gets natural daylight (with a box beside to the tank to try and block most natural light)
Diy Co2: 2x1L bottle with 200G sugar, half teaspoon of yeast. Alternate changing a bottle each week
Stocking: 5 guppies, 3 corys, 5 rosy tetra, 4 scissortails, 5 Harlequins, 1 dwarf gourami, 2 snails, 1 dwarf otto.
Filter: Interal AquaManta XL with circular ceramic media and sponges, dipped in old tank water ever other week to clean.
Maintenance: 2ml Plantamin every other day and 4 ml of EasyLife EasyCarbo every day. 20% water change each week. Fish are fed every other day and eat all the food within 5 minutes.
Temp: 27 C
Plants: A bunch of hygrophillia, some tall grassy stuff, floating plants, java moss on bog wood and a bunch of other plants (can provide pics if it will help)
 
 
 
Here is what I usually get from my test results:
 
PH:7-7.5 (depending on time of day tested)
KH: 4-5
GH: 5
Ammonia: 0
Nitrit: 0
Co2: according to KH/PH test it is around 15ppm but I don't trust my test to be accurate enough for this. Drop checker wit 4Dkh + blue seems to be just about turning into green but not very obvious.
 
And the problem
Dark black spots on leaves of hygrophillia, particularity around the edges. Most of the spots can be wiped off by hand but it just keeps returning. I have also noticed a small amount of BBA on the tip of some of the leaves recently. Some of the other green plants have started to go a little thin/transparent and 1 or 2 even starting to go yellow.
 
My Understanding
Now I understand that Algae is usually caused by excess lighting/ nutrients. I stopped dosing the plantamin for around 3 weeks and noticed no difference in terms of algae. Plantamin doesn't really tell me what is in the bottle so I am looking at other products (possibly easylife profito) but should I also be dosing macronutrients along with these ferts?
 
 
Thanks for all your help in advance because this is driving me mad! I love having real plants but fake ones look more tempting each day.

 

[BerryAttack]

the black stuff on the leave is most likely algae, i usually get it on the leaves closes to my lights. 
if you having an algae issue you can get root taps that are placed under the gravel/sand for the roots of the plants, this'll help limit excess nutrients from going to the algae. 
if you really don't like algae, you can add a bunch of snails to your tank ( the ones that come with plants and just multiply like crazy) at first it'll be an explosion of snails, but they will eat algae and left over foods. then when there is not enough to sustain their numbers they will die. i personally don't mind snails, helps keep algae away  
 
i have hygrophila in my tank as well, they can be grow in low light, but i have a medium to high light tank and it does great.
depending on what grass type you have will determine if it is doing as well as it should because of the light you have.
with your lighting you're getting around 1.8 WTG, this is usually best for low light plants.
the melting of plants and dying of the leaves if normal, just remove the defected leaves from the plants... it'll look a little bare at first but it'll come back bushy and healthy. if you don't remove the leaves then the plant is still putting energy to the leaf and then not enough energy towards new leaves.
 
now with your fish, i would say that you are over stocked.
the dwarf ottos are best to be kept in groups of 3+ they are social fish.besides that i would say that your fish numbers in groups are good, but on the over stocked side. this just means you need to keep up maintenance and not skip out.

 

[daizeUK]

Plantamin does not contain nitrates or phosphates so that could be your problem, unless your tap water is naturally full of them.  Your plants need these macro ferts to make use of the carbon you are pumping in.  I suspect the BBA also indicates that your CO2 levels are insufficient/unstable.

 

[snazy]

Now I understand that Algae is usually caused by excess lighting/ nutrients.
 

 
No, it's caused by excess lighting/lack of nutritients and co2.
 

I have also noticed a small amount of BBA on the tip of some of the leaves recently. Some of the other green plants have started to go a little thin/transparent and 1 or 2 even starting to go yellow.
 

 
This is a typical sign for lack of CO2/flow not distributing the CO2 everywhere.
 

Plantamin doesn't really tell me what is in the bottle so I am looking at other products (possibly easylife profito) but should I also be dosing macronutrients along with these ferts?
 

 
Yes, you can't do without macronutrietients when you are supplementing CO2. They are called macro because plants use them in larger amounts than micros.