None of my plants are thriving

I'm at my wits end with plants in my main tank. My anubis and swords are yellowing, my ambulia and baby tears are covered in brown algae (glass is clean though), the two val I recently bought seem to have melted away to nothing, one of my banana lilies just died and I can't keep floating plants alive either. I've also tried guppy grass and cardamine with no luck. Only thing that seems OK is java fern :-/

Tank finished cycling in June, plants seemed good for a few months, but going downhill now. Not sure what I'm stuffing up!

I have plain gravel substrate but put a dymax root tab in for each sword and clump of stem plants, plus I dose LCA all in one liquid fert 1.5 pumps 3x week.

I have an AquaOne Lifestyle 157 all in one tank, so I have little control over the lighting other than the timing and with the fully enclosed lid and tank length waterfall filter outlet it's pretty humid/drippy so I think that could be why the floating plants don't cope, but I don't know what I'm doing wrong with the rest. Too much fertilizer? Not enough? Missing nutrients?

Weirdly/sadly I can't keep snails alive in this tank either - they retract and never come back out of their shells once put in here. Fine in my other tank, so unsure why. Unsure if related?

Any advice very welcome!
(And thanks for reading my essay lol)


EDIT: Sorry, forgot!

ammonia 0
nitrite 0
nitrate 40-60 (pre water change, will test again tomorrow)
ph 6.4
temp 25 C

We have 3 honey gouramis, 2 otos, 5 corys, 10 cardinal tetras.

 

Ok are you doing the 50% water changes. That does seem to be a good liquid fert. Root tabs only for the sword. Your tank looks good. I’m betting the light isn’t the best for plants. Is it led? Next the snails are dying from the copper in the fert. I think you may be dosing to much. I only dose once a week. The anubias and swords don’t need lots of light but I do think the baby tears need good lighting.

 

My Anubias grew three feet long in a ten gallon tank in a corner with a single LED so I doubt it's the light. Swords are kind of known for liking light and my tank is 16" tall now, so the light doesn't hit them. Tetras like to nip at the roots of floating plants. That might be why that's happening, especially if the plants are moving about in the current.
I have a low light aquarium and honestly the only things that have taken hold are the anubias (now in a bunch of parts), my bushy cryptocornes and my sußwassertang.
Ooooh, also, the roots of the anubias really ought to be in the gravel. Not the rhizome though, the stemmy bit the leaves grow from.

 

Carbon dioxide will perk everything up nicely.

 

Thanks all. Yes, we do 30-50% but lately closer to 50% in line with fert instructions. You're right, the light is not ideal and it's over the front half of the tank (filter in lid at the back) so perhaps not enough for the swords. I kind of expected that, but the anubias doing poorly is worrying me?

I've never had anubias with their roots in the substrate and they've been fine in my old tanks - these were all bought attached to the tops of driftwood. Not sure there's a whole lot I can change easily there.

I'll cut back fert to 1 a week and see if that helps :-/ feels counterintuitive but worth a try haha

Thanks!

 

You could also continue on the same fert schedule, but decrease the number of "pumps" you put in.

An acidic pH isn't great for snails.