Almost the exact same thing happened to me. Couple months ago I switched from flourish liquids to EI from GLA. Within a week my ludwigia lost its color, began dropping lower leaves, and exhibiting stunted and twisted new growth. The only other two plants affected were ammannia gracilis and mermaid weed. They both did almost the same thing. All my other plants responded well.
I was told by the experts it was lack of co2, so I increased it. Didnt help. Logically it made no sense to me that it was a deficiency in anything, because the response was too dramatic, and it happened too fast.
Through trial and error Ive concluded that it's caused by csmb. I can do a big water change, skip the micros for a few days and things start looking better. Dose micros again and boom, next day things are headed back the other way. Even 1/2 the recommended dose seems to be too much.
In my particular case, I have huge amounts of Osmocote+ root tabs in my substrate, which is inert blasting sand. I suspect that a good portion is leeching into the water column, and the added csmb is causing a toxicity of either iron or some other trace.
It's now been 10 days with no micros and three 60% water changes. Things are finally getting back to normal. Ive continued to dose the full amount of macros the whole time, since none of that is known to have negative effects from overdosing.
I doubt this opinion will be a popular one. Nobody seems to want to hear the words overdose and EI in the same sentence, LOL. Nevertheless it has been my personal experience. I chalk it up to having used way too much Osmocote+ in the months leading up, at least too much to have in combination with EI levels of trace.