That just goes to show how little experience I have, I guess. How do you do it?
Anyway, aside from what you already have, Ludwigia repens is supposed to be okay without extra ferts and CO2, it just might not have much color. Moss also will do well, and hornwort, anacharis, rotala, and bacopa. That's all I can think of.
as long as I don't over feed I don't have a problem.....Oh did I forget to mention that I have a 45 gallon sump absolutly full of ricci over the top of the water. That probably helps out a lot for me. I don't need color, it would be good but not needed. I just don't want the plants to not do well and look like crap. My 29 RCS tank has about 2 watts per gallon and it just thrives with no ferts or CO2. Had some hair algae once when I over fed, the shrimp liked it though lol.
It appears to me that an aquarium can acclimate to light fertilizing if you give it enough time. For those of us using EI fertilizing PPS Pro seems like no fertilizing at all, but tanks work well with that system. And, if the plants continue to grow, don't accumulate dead plant matter, and the light intensity isn't really high, you can even avoid algae, with luck.
What light or lights do you have on the 75 gallon tank, that give 1.5 to 2 watts per gallon? (110 to 150 watts?) And, is the light fixture sitting right on the top of the tank? It could be that the effective watts per gallon is such that you have low to moderate light intensity.
Incidentally, almost all plants do better with more light. "Low Light" plants are those that can tolerate lower light intensity, but they don't prefer it.
That is about 3.5 watts per gallon, unless you have no reflectors at all, then it might effectively be down near 2.5 watts per gallon. Plants will suffer with that much light driving them to grow fast, but without the fertilizers and carbon needed to do so. Usually, the most competitive plant will hog all of the nutrients and struggle to grow, while the others just die.
Like I said this isn't a new tank and the plants that are in there now are doing fine. Some have been in there years the rest months. I was just looking for some suggestions as to what else might work.
In 1.5 to 3.2 WPG with no CO2 or Excel in 5 different tanks, I am growing hygrophila (Angustifolia, Corymbosa, Difformis), Ludwigia (Cuba, Repens), rotala (indica, vietnam), Mermaid Weed, Purple Cabomba, Limnophila (Aromatica, Aquatica), Echinodorus Bolivianus, Java Fern, XMas Moss, Anubias Nana, Bacopa Caroliniana and several types of Crypts.