Welcome to Tropical Fish Keeping forum.
There are actually several contributing factors at play here. Starting with the light, as other members said, it is bright and on for along time.
You are going to have difficulty balancing this much light (intensity here) with nutrients, especially carbon (CO2). Can you remove one tube and still have the other light? We can discuss other options if not. Certainly reduce the duration, no more than 8 hours with this much light.
Eco-complete is questionable. It is basically identical to Seachem's Flourite, and I have had this in my 70g for more than 15 months and am very disappointed with the results. Won't get into all that, but first off the substrate nutrients will only benefit substrate-rooted plants; this means floating plants (which are important for several reasons), plants attached to wood or rock, and most stem plants will derive no benefit. And for the substrate-rooted plants, there are some nutrients that aquatic plants take up via their leaves rather than the roots. So what all this means is that with or without an enriched substrate, you need liquid fertilizer. Flourish Comprehensive Supplement
or Brightwell Aquatics' FlorinMulti
are both good. Twice weekly will probably be needed, even with one tube. And this brings me to the water chemistry.
RO water is "pure" so the hard minerals particularly are missing, and there is not sufficient in any of these nutrient sources (substrate, liquids, tabs) to compensate for soft water. I know because I have almost RO water coming out of my tap and I need to add hard minerals (calcium and magnesium primarily). You mention mixing in some well water, so that may provide this, depending upon the mineral in the well water. Any idea of the GH (general hardness)? May have more to offer when I know this.
Temperature stood out, 80F is high for some plants and many fish. Fish species aren't mentioned, so do you have some that require this warm a temperature? If not, i would lower it; fish will always be better at the mid-range of their preference because the metabolism functions slower at lower temperatures so the fish's energy is not being sapped.
New plants will frequently lose existing leaves. They need time to adjust, plus they may have been propogated in the emersed form and this requires a change in leaf structure for submersed growth. We have plant profiles 9and fish), second tab from the left in the blue bar across the top of the page, so you may find some further info there. The plants you mention are mostly included.