I live in Florida I grow all types of Citrus. If you go to Lowes look for

Ironite 375-sq ft Plus Lawn Fertilizer (12-10-10) runs for about $5.97 that should solve your problem. I used that as a Secondary Fertilizer. You can go online and read about it the best thing is that it includes plant nutrition that doesn't usually comes with standard fertilizer. Just remember the more nutrients the Citrus seedling get's the healthier it will gorw. The first year of any Citrus seedling grows slow because it's developing it's roots. Once it completes it's first year the plant will grow very fast. I have over a 100 of them between Valencia Orange, Mandarine, Key Lime, Myers Lemon, Mandarinquat that are wrapping up it's first year and are ready to burst a 6 inch brand new bark. All my other's have exploded. Also you might want to consider Organic Pesticide and Fungicide. I used Bonide 32-fl oz Copper Funicide $ 9.97 and Bonide Captain Jack's 32-oz Garden Insect Killer $ 8.97 all these items can be purchased at Lowes. They protect against Canker, Leaf Miners, Japanese Beetles, Fungus, early and late Blight, Fungal Diseases etc. I use organic potting mix. Never spray edible plants with Peticide that causes cancer these spray's will transmit to the edible fruit or citrus causing human effect including cancer. The one's I mentioned are organic and will not burn the leaves on the plant. Also Garden Safe Neem Oil Concentrate is helps protect new growth from leaf miners attacking new leaves.