WOW! AWESOME PICS!
That's excellent color saturation. How vibrant! I'm jealous (of the tank and your photo skills).
You gotta tell us how you got the pics to post. Did you do something unusual?
About the stem plants losing leaves: Are all stem plants losing leaves or only on certain plants? If it's on certain individual plants, I'd say it's probably that the plant "wants" more light than it's getting or the stems are "old". Old stem plants get "senile" from the bottom up. They lose the ability to transmit nutrients up and down the stem. It get's harder and harder to grow leaves, photosynthesize, etc. They lose vigor. Next time you prune, keep and replant the stem tops and discard the bottom and roots.
If a lot of stems (or most stem plants) are dropping leaves, it may be a toxin issue. Maybe, an increased schedule of water changes and use of carbon, in your filter, can get rid of it. If you use it, add Excel. It hinders a lot of algaes and adds Carbon (a kind of artificial CO2). In my tank, Excel helped when growth rate slowed. The density of my plants' leaves increased, too.