The longer growth between the leaves of the ambrosia/ cabomba lead me to believe that the light isn't sufficient so the plant is reaching a bit. Macros/ micros would help but use very little in respect to the overall volume of the tank as these plant normally grow like weeds without much effort.
Try spreading the plant apart so that the individual stems don't shade each other as much as a test. Trimming also makes the plant sprout new growth so consider doing a bit as well.
Looking back at the photo, the tank certainly is a low light tank so there wouldn't be a growth explosion to be expected.
The Aquatic Plant Society Curator of the NY/NJ/CT LFS & CO2 Directory
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