Dwarf Sag is an iron hog and, IME, also likes to eat more nitrogen that other plants (low nitrogen can cause transparent leaves). Make sure that you are dosing enough iron and, although I generally don't favor root tabs, in this case it may help to add some root tabs, such as Seachem, to see if the focused nutrients will reverse your fortunes.
If you want a deeper look at your setup, then please provide as much of the following as possible:
- Light (make & model): ideally, PAR and PUR reading at the substrate and photoperiod?
- CO2 setup (if any) and, if you inject CO2 (pressurized or DIY?), what is the CO2 ppm level and how is it measured?
- Current NO3, PO4, GH, KH, pH and TDS readings and which test kits/devices are used for each?
- What you are dosing (product and quantity), in terms of ppm, and how often?
- Substrate type and how long has it been in place?
- What is your filter setup?
- Cleaning regimen (filter and water change frequency and amount)?
- Circulation: surface rippling and are all plants gently moving from top to bottom?
- What is your water source and do you use a water softener?
- What is your tank size?