Hi and welcome to AA!
I would say your tanks about full now. I wouldn't add any more fish. shrimp are fine though.
Did you just let the tank sit for a week then add the fish? Unfortunately that's not cycling. To cycle you need an ammonia source. In this case the fish. When you added the fish you stated the cycle. Can you test your tap water for nitrates?
There is alot of debate about whether carbon removes fertilizers or not. Personally I don't use carbon in any tanks so i don't really have an opinion. It only last a week or two then needs replacing. If your tanks well maintained there is no need for it.
Some reading for you.