Plant Deterioration - Diagnosis & Suggestions?

See https://forums.thinkfish.co.uk/fish-tank-plant-advice/useful-plant-diagnosis-charts/
And http://www.seachem.com/flourish.php

It looks like a potassium defficiency to me but I'm only going off what I can see on the bottom most image on the charts and the fact that flourish doesn't contain any.

Seachem Flourish (with nothing else in the name) contains trace minerals, also called micronutrients. Potassium is a macronutrient - it is the K in NPK - and can be dosed separately.

I don't know much about plants except the few I grow, but I do know that a lot of plants go funny (melt) when first put in a tank, particularly crypts. And that as Trenchy says, a lot are grown out of water and lose their leaves when put into water - but they do grow new leaves.

THIS POST, AND THE 6 POSTS WHICH FOLLOW IT, HAVE BEEN MOVED FROM "REJUVENATING NEGLECTED TANK" THREAD AND MERGED INTO THIS THREAD. 

Add the plant fertiliser the day after a water change. The dechlorinator will contain a chemical to bind metals so it is better not to add both at the same time.

Wondering if this is where I'm going wrong too. Change of regime from this week onwards.

Yes, @Littlefish - that's exactly where I got them from. That's all very interesting - thanks.

The last batch did particularly badly, and some from the previous batch didn't do very well either, so I e-mailed them to seek advice and have had a helpful reply, including that very point about a small amount of fertiliser daily. Although I've only recently got the Seachem Flourish, and it doesn't contain the macro nutrients given the presence of fish and fish food for NKP, they recommend an all-in-one product called TNC Complete which contains macro and micro nutrients, as well as carbon/CO2. I seem to recollect a risk with CO2 overdosing to the potential detriment of the fish - is this a risk with all CO2/carbon products? Would fertiliser tabs be of any use when my plants are either tied to wood or kept in their plastic pots (due to only having sand as a substrate)?

I agree with Sue with regards to slow growing plants not needing carbon.
For a few of my more heavily planted tanks, and especially those with bigger/taller plants, I generally go with around 1/7th of the liquid fertiliser daily, along with probably less than the required amount of liquid carbon. I'm aware of the issues with liquid carbon, and tend to err on the side of caution with that. So far so good with my gang.
With your plants in pots, do they still have the rockwool around them?

With your plants in pots, do they still have the rockwool around them?

Yes, I keep them as they come ie still in their rockwool.

You can plant in sand, lots of people do very successfully. If you keep them in pots, they need to be planted in something, along the lines of growing garden plants in containers. Though no garden compost in a fish tank 

I have enough trouble trying to get the plant pots to stay upright, that I think any attempt to have the plants staying upright in the sand is going to fail. Is keeping them in their rockwool alright or ought I to be transferring them into something else?

I was wondering if removing the rockwool, and putting the plant back in the pot with some gravel, might give the roots more room and allow more water flow & more nutrients to the roots.
I've got amazon swords in the axolotl tank which I've attached to decor, rather than planted, because the axolotls kept digging & moving the plants when they were in the substrate. I don't know if it's worth trying that with your plants, it probably depends on how delicate your plants are.

Thanks, all - very helpful. I think I have sufficient supplies to make this do-able (once I get some root tabs).

In terms of the macro-nutrients, is this a moment of wishful thinking* impairing my thoughts or might the addition of more fish (and thus fish food) actually help the situation further?
[*following having noticed some tempting ember tetras recently]

True...    The only issue is that, with what is realistically a water volume of 45 litres (decor and lower waterline taken into account) and oversized filter, 8 ember tetras (realistic minimum) would push the stocking limit to 100% which is too close for comfort; while some folk could get away with this, would be just my luck that there'd be a power cut or that one of the two filters would malfunction.

I would say you could consider the ember tetras once the plants are growing well as they we'll boost "filtration".  You are right that more fish and more food equals more macro nutrients. You might also wish to consider dosing micro nutrients to get the plants going.