Holes on new leaves

Hello! I's my first attempt ever to ask something in a forum, so excuse any mistakes.

I have a small aquarium, ~54 liters of water plus the substrate, which is a mixture of Flourite, Volcanit and JBL AquaBasis plus. The tank is running one year now. I have one power compact 24W daylight lamp, one 15W Dennerle Plant lamp and a standard 24W mini compact daylight Philips lamp. At first I had serious algae problems, being a newbie, but now it's under control, given the fact that I use the standard lamp, which I think promotes algae, but I have no room on the hood for a bigger specialized lamp. I use all Dennerle fertilization products, especially A1 Daily, plus Flourish.

The water parameters are 7.2 pH, 9 KH, ~15 GH and with a DIY CO2 supply, about 17-20 ppm CO2. The nitrates are about ~15 ppm and nitrites 0.

So I have a problem with holes on leaves. Strangely the holes are on new leaves and as the leaves grow, the holes grow with them. I attach a picture to see for yourself. Also sometimes the holes are on the edge of the leaves, so the leaves grow misshaped. This happens on every large leaf plant I have, on Anubia and on Hygrophila corymbosa.

Although I have spent a lot of money to setup, I'm trying to keep the cost down. So I only have a pH, a KH and a CO2 test, no test to measure phosphates or iron. So I sometimes overdose nutrients, but I water change ~40% every ten days. And BTW the tank is fairly stocked with totally about 25-30cm of fish.

The picture shows a 5 days old leaf of Echinodorus 'Python'. The hole just grew with the leaf.

So do you think that something is wrong with my plants? Should I change them? Or something is wrong with my setup, excess or lack of nutrients? If I find a solution to this, I will probably solve all my tank's problems!

I'm looking forward reading your suggestions. Thanks in advance!

 

Thanks for the reply.

I forgot to mention that I'm using 1.5 ml of Excel daily. I thought that it would fill the gap of missing CO2 when needed. Probably I'm wrong.

I already made another bottle of yeast to see the reactions.

 

Hello again! First of all, thank you all for your interest.

Sorry for the delay but I tried to follow your suggestions.

Firstly, I understood that everyone, sooner or later, abandon the yeast technique!
I think that myself will be the next....

So after a lot of experimentation I managed change the one bottle with two new ones.
I use gelatin in the mixture, so yeast has no direct access to all the sugar.
But these two bottles started making Co2 like crazy!!
The pH dropped to 6.6!!! With a KH 8!!! According to every calculator, that's a lot of Co2!
I'm using a pump at the bottom of the tank to diffuse Co2, which spreads it into very fine bubbles(really small bubbles, like a ceramic diffuser) to all the aquarium water. But maybe that's the first time pH drops so low.
At night I shutdown the pump and big bubbles just go straight to the surface.

So my first observation is that one bottle is sufficient, as long as I do the mix right.

My second observation is that I really cannot achieve stability. Not at least with my abilities and knowledge(and my patience!). Co2 is balancing whatever I do.
I do large water changes, Co2 goes down.
I use wrong ingredients in the mixture, Co2 is not enough.
I use correct ingredients in the mixture, Co2 goes high!!
I have no time to make new bottles to replace exhausted ones, Co2 goes down.
No way to maintain stability. And such unbalanced condition, I think makes my plants and of course my fishes unhappy and anxious.

So I'm already looking to find a good and cheap solution for proper Co2 source.....

To return to the subject, the holes on the leaves are definitely related to Co2 up-down.
BUT I have suspicions that they are also related to high kH. I've read that all plants need no more than 7 kH. Do you think that lowering the kH around 6 will contribute to this problem? Have you heard something like that?

Holes on leaves may indeed become due to snails, but (unfortunately) there are no snails in my tank. Just three Caridina Japonica shrimps. But there is no way to be their work, as I can see the holes to "born" with the very young leaf.

Again thank you all, I hope you can understand(and forgive) my bad English!