New But The Same

Hey all so I started having problems with my fish tank...three fish died in one week. Still don't know why. But I decided to do a large water change...My plants were also having issues..they were starting to die off...so I changed the light and got a better one...I wanted to remove the fluval plant substrate from the back because it was constantly getting in the way so I decided just to do a full rescape and remove the fluval plant substrate to just make it all sand again. I figured that, while I'm at it, since my ten gallon tank was old with lots of buildup at the top (from the hard water down here) that I would just get a brand new tank since I was taking pretty much everything out anyway...so about 100 dollars, 7 hours, and lots of work later, this is what I came up with...Unfortunately since I did such a big change (and had to rinse out the substrate like crazy and put new substrate in) I think I might have to go through a mini cycle...lots of water changes here I come!

Ten gallon

Fish
Balloon molly adult: 1
Balloon molly fry 6-7 months: 1
Ballon molly fry 1-2 months: 5
Cherry shrimp: 2
Ghost shrimp: 2
Assassin snails: 2

Plants
Hornwort
Pygmy swords
Italian val (just little sprouts)
Java fern: 2
Anubias: 2
Ozelot sword: 1
Java moss

Lighting: 15 watts/T8/5500K
Ferts: Dosing every other day with pferts micros, potassium, phosphorus, and nitrogen
CO2: none

Please, any suggestions/criticism is welcome...And a few questions: could I put some pygmy corydoras in this tank? and do I need CO2 or is my setup fine?

edit: I didn't know how to change the title of my other journal so I just decided to attach it to this one...and since I'm starting fresh I figured a new journal would be okay