Give it another 2-3 weeks, then reassess. You could get a drop checker and 4dKH solution to check on your CO2 level. Since the tank is cycled, there's no need to test for much of anything unless you want to watch nitrates.
One suggestion I have is to do a bit more with ferts. You say you use liquid ferts, but what type? With higher lighting and some CO2, you'll need to dose nitrates, phosphates, and possibly potassium sulfate (depending on your tapwater parameters), and definitely trace. If you're using Flourish Comprehensive, you're dosing trace, but not doing much for N, P, or K.
If what I'm talking about regarding fertilizers doesn't make much sense, there are a bunch of links for fertilizers. But, basically, it will probably be necessary to dose KNO3, KH2PO4, and possibly KSO4, as well as Trace.
On a down note, I'm not sure if the Nutrafin system will be enough for CO2. You might want to add Excel to the mix. Still, wait a few weeks and then decide.
What Kevmo said is spot on. Your lacking in nutrients. If youd like to save some money and make it easy switch to dry ferts. There are several places to get your dry ferts. I bought mine from Bobs Tropical Plants. Get the startup kit. Its $20 bucks basically and has everything your going to need. Its the Plantx CSM+b and NPK. For what you have the CSM+B might have enough Iron in it. I would try dosing your tank according to EI dosing. ALSO get some good root tabs. I like to use the Osmocote plus root tabs. They are cheap and very complete. Also can be bought at Bobs plants or here in our Swap and shop. Your Crypts and any root feeder will like those below them in the substrate.
One of the other things I would agree with Kevmo is the Co2 kit you have may not be enough to make a impact. If your going to do a "DIY" type of Co2 and not true pressurized I would do it on a larger level that will make a difference on your tank. OR just bite the bullet and do Pressurized and it makes it even easier.
What is the light you have? you mentioned T5, But is it T5NO or HO or what? What is the bulbs in the fixture? are they plant rated spectrum's?
Having test kits isnt a bad thing. I would test for PH, Nitrates, Phos, and iron. You could test for Ammonia and Nitrite. But not normally a worry if your tank is cycled. As far as knowing water hardness and DKH you could easily call your local water and find out.
One last tip. Get more REAL plants and get the fake stuff out. Most people find that when they load the tank with more plants it does much better then if its got just a couple.