advice to new planted tank things

Hi, I am new to this forum and fairly new to the aquarium thing- but I LOVE it!! Already went from none to a 1.5 gal/10gal/20gal and a 100 gal...in about a month or so. Well, I have jumped in and went crazy on a tank with the plants and now that some of them are starting to brown I am wondering what I can do to salvage things... I obviously didn't do any research I was dumb and listened to my dad who seems to have lots of plants in his tank and all seem to be doing great. this is my tank
I have a 100 gallon that is Cycled. The Nitrates are about 10
I bought the tank used and 2 Power glo 20W bulbs that say K 18,000 on them that I have turned on 12 hours a day (is this too much?)
I am using good ol' tahitian moon black substrate mixed in with a some grey sand like substrate that I initally bought thinking it was black- nothing special - certainly not specific to plants (i would've got this eco-stuff if I would have found some and/or even knew it existed)
I have various plants not REAL sure of the names- Moneywart i think is one and seems to be doing rather well....my favirote is some sort of swordplants- quite a few of them and they are getting brown spots all over...maybe even burning up on the leaves- How can I fix this? Should I cut off the brown like you do with regular plants? I also have 2 mondo grass plants that I read on wetweb that are NOT good for underwater plants at all- and i am considering taking them out all together- should I? Yes, I just walked into a few different pet stores and bought a bunch of plants they claimed were meant for aquariums- I wanted my fish that I already had to have a good enviroment ASAP. I also have a bunch of little grass-like plants that I bought as these 3 blade bundles and 4 purplish/red plants and gee I WISH I wrote down the names. I guess its time to research.
What sort of fertilizer should I start using and should I be testing my water for CO2 or something? I have been looking for a test kit to test iron and other plant related things but haven't seen any. I know I probably have a big old mess and any assistance would be appreciated. I just want a highly planted tank and wanted it as quick as possiable. I am actually STILL trying to get it. And it would help If I knew a little about keeping them healthy. I really want a tank full of ground and floating plants and any assistance/recommendations for getting there ASAP would be greatly appreciated. MUCH THanks for reading my rant

I dont think I have the first one. It doesn't rub off it looks like its "burnt" Actually let me post a pic (if Ican figure it out)

well, that s the thing Im not exactly sure what to test for as far as nutrients. All I know is my Ammonia is O nirtrite is 0 and Nitrate is 10. i haven't seen test kits for iron or anything - I think I am needing to add more substrate tommorow and get some root tabs it sounds like. I am wanting a WHOLE lot more plants anyways-
I was holding off on the substrate because I wanted to make sure that its an appropriate kind to have a "planted' tank. You know for 250$ camera it sure does take crappy pictures. Sony cybershot....maybe i just dont know how to use it.
I replace 25% of my water biweekly-sometimes weekly

thanks for the tip...i will DEFINATELY try this....i have tried to sit down and read the manual but with a 5 month old always striving for my attention its not easy.