Alright sorry to hear bro, here's some info that might help.
Lets just assume you have the following:
-All the Ferts you need
-efficient CO2 delivery method
Feel free to confirm what you do and do not have. Please provide more specific info on your tank if you can. For now, follow these steps:
1. Clean up the tank as much as you can. Manually remove algae, remove dead decaying plants, wipe algae off glass.
2. Do a 3 day blackout, chances are things are pretty bad in the tank so do a 50% water change, drop in an airstone, and black the tank out of absolutely 0 light for 72 hours. Add excel if you want, but if will only help as most plants aren't sensitive to it unless you got like vals. Do a 50% water change after the blackout.
3. Once done, add more plants. I mean a ton more. Get em from ppl here or your LFS while the blackout goes on. Anacharis is sold at many pet stores that grows like crazy and love nitrates, will melt to excel. Water Wisteria works well as well as other fast growing weeds. Floaters also work but heh, duckweed you might never get out later on so your call. It's ok if you do not want the plants later, lets just focus on getting the tank back in order.
4. Lower the light intensity a bit, and keep total light time to max 8 hours. Possibly put in a 1 hour siesta or break after 4 hours to allow co2 to build up again. Make sure CO2 kicks in 1 hour or so before lights and then stop co2 30 mins before lights out.
4. Follow a decent dosing regime like EI or just make sure you got your macros (NPK) and micros covered. Might want to make sure you have decent GH, but chances are your tap is fine unless its RO or super soft.
5. Crank the CO2 up to acceptable levels. Slowly adjust this. Find a level that fish are ok with, then slowly increase it over weeks, maybe 2 turns a week, no more than just a little bit. May take a week for fish to show stress.
6. Be patient and wait. Try to maintain stability.
Also, salt + plants =
plant. Add in elevated temps =
plants. Next time get a quarantine tank and treat them there.
EDIT: Forgot to mention have decent flow.