To be honest it should not cause an issue but you can try to get the ration closer to at least 4:1. And doing more research as long as you are not limiting any of the trace nutrients it really is usually co2. High co2 fluctuations can cause issues. Its MUCH easier for co2 to fluctuate say 10 times than any other parameter in the tank stressing the plant causing issues. Are you sure your co2 is consistent? What is it at when lights come on? Does it stay consistent during the day? Notice any co2 swings? Does drop checker stay same color throughout diff locations in tank? Without looking further back in your post how are you diffusing? Is the flow good enough to evenly distribute the co2 equally. Reading a ton of Tom Barr's articles and threads he has proven many times that when many think its ca/mg/k its actually co2 that somehow or another is causing the issue making it look to be ca/mg/k.
Back to the ratio according to Tom Barr he said it was never really proven that being that far out of ratio causes a problem. Just make sure that neither ca or mg are limiting and you should be fine.
I would really look closely at your co2. Use a PH pen and get accurate before/after measurements throughout different locations in the tank. Test close to where co2 comes in at and on opposite side. Does drop checker stay consistent color ie green/yellow? I know drop checker is hard to use as its like a 2 hour delay. Again cannot stress enough really check your co2.
Also do you have lighting dead spots where the problem plants are at? Is it just one spot where the plants are having problems or spread out throughout the tank?
I will quote what Tom Barr had said in a few different posts about similar issues
"Mg is more common for issues, many suggested it was K+(Potassium), but CO2 and Mg will influence that more than Ca which tends to rarely an issue but an oft loved excuse for poor growth.
High levels of NH4+ and Mg++ will block K+ far more than K+ ever will.
And there is research to support that.
So do not go nuts with Mg.
You just need a little bit and the ratio itself is not going to cause much issue if the Ca is high. 10-20ppm is more than enough.
Regards,
Tom Barr"
"I'll give this a whirl.
I like the Rotala and it does grow back fast when happy.
What might be interesting is focusing on the KH vs Mg.
I know many folks that have rather high GH's, many from dosing SeaChem Eq and in a number of cases they have Mg over 10ppm but an associated higher level of Ca as well.
Ca/K/Mg/NH4 blocking all appears to need to be much higher concentrations typically found in pore water to start to get blocking. But species to species difference may play a larger role.
I have found the Luwigia cuba to stunt much like the R wallichii in the hard KH/GH's, but teasing apart which is causing what requires more grow out and then changes to the Mg, KH and Ca levels.
In general, if there is a GH issue, lower Mg is typically the reason if the GH is already high, it's virtually unheard of to find high Mg and low or limiting Ca levels if the Gh is 3-5 degrees or high.
Many folks have high GH's and does well with Rotalas and Ludwigia cuba.
It might be evidence of a ratio being important even at low concentrations.
Regards,
Tom Barr"
"but your new routine adding a little bit of SeaChem Eq each week will address the issue(which is Mg limitation), we found this out about 10 years ago in the Bay area using this product.
Many thought it is was all the K+, which was all the rage back then.
Some thought it was the Ca, Steve Dixon wondered if it was the Mg. He's alos the guy that found out I had such high PO4.
He had so many things right on looking back, too bad he's not active any longer.
I'm about ready to torture some wallichii also. Bring on the salts!
Regards,
Tom Barr"
"I tend to suggest a few degrees of GH for soft water, about 3-4 at least using SeaChem EQ or the Gh booster, folks with harder GH waters may need some Mg or Ca to balance things out so neither is limiting.
I think you can approach it that way, using just GH and adding a bit more with a balanced product or................you can analyze GH individually into the Ca and Mg sereprate nutrients.
Simply because you do not test, does not mean you need to know what the ppm of Ca/Mg, only that you have enough to prevent limiting conditions.
That's the real issue for 99% of aquarist, not confusing themselves with test kits/methods.
Why test unless there is a problem?
How do you avoid such problems to begin with?
Pretty straight forward.
If you suspect K+ is limiting, then add more K+ and see.
You do not need to test the K+, you can if you want, but you do not need to do so to know the K+ is limiting or in excess. Simple calculators will tell you that.
Regards,
Tom Barr"