I would not pug it anymore like Jeff said, it needs some leaves for photosynthesis. It has been really cool lately in SoCal and my inlaws longan hasn't grown much in the cold weather. Lychee and Longan grow in spurts. You can sometimes see little bump like protursion like zits on the branches before new growth pops out. My inlaws longan wasn't doing very well in a pot for some reason but once they planted it in the ground, it started doing really well. There seems to be a consensus that your plant is not getting enough sunlight. I personally like to give my fruit trees Fish Emulsion and liquid kelp at very very diluted amounts. I think the brand I use is King Neptunes which is a combination of fish and kelp. I dilute it about double of what the instructions recommends. Your plant probably wont even need any fertilizer until it has another growth spurt but a diluted feeding for a plant you've had for 9 months without any fertilizer shouldn't hurt. The trunk of your tree around the base area seems a bit moist. May I ask why the cardboard is around your tree? In my opinion, the daily transpiration/evaporation cycles play an important role for the trees rhizosphere. By keeping the cardboard there, you may be holding in too much moisture and not allowing the soil to breathe properly. This may cause fungal or other problems. Your tree still looks like its in good shape and with a little TLC, it should be able to branch and leaf out nicely. Let us know how it goes!

Hi zetterberg, The curling upward & chlorosis on older leaves looks like magnesium (Mg) deficiency symptoms. It is not fatal. I am guessing that you have been using a good deal of calcium (Ca) in your fertilizer, since we are always paranoid about BER. Also, when a container medium is "limed" to adjust pH, this technique can introduce several Ca variables. (Not subject of this post.) There is a problem associated with Ca, which is usually a booster of mineral uptake - but not Mg. Mg uptake is less with excessive Ca present (one reason why symptoms take time to show up = it takes time for Ca to build up). Since Ca is not a fast moving element it is possible that in a SWC it is accumulating in the root zone, from wicking into the growing medium. This Ca can the alter the root's membrane surface & bind to reactive sites in a way that affects permeation of Mg. (But the same Ca behavioral properties encourages many other ions, like crucial potassium or K, uptake.) So, please review your level of Ca use, to see if you are using too much of a good thing. In a SWC the fertilization technique (ie: wicks up depending on growing medium used) may be hard to alter, but the fertilizer ingredients can be adjusted. Flushing of the growing medium would be possible to do; but quite inconvenient an extreme if leaf Mg deficiency symptoms are not becoming rampant. An effort to foliar feed Mg may or may not be effective, opinions on the technique vary. Foliar feeding excessive Mg that is allowed to drip down into the growing medium may or may not (TDS problems) be desirable. Poster named structure indicates his top watered container tomatoes do not have these symptoms, but tomatoes in his SWC do. To me this indicates his top watering precludes the Ca from accumulating in the tomato root zone & so no Ca antagonistic affect occurred with Mg; unlike symptoms seen in his SWC tomatoes. Dirt growers have an open eco-system so tomato crops are less prone to this Ca/Mg inter-action problem. For those with high Ca content in their irrigation well water &/or calcerous (many island land is upthrust coral) soils the symptoms of Mg deficiency are possible.

Definitely an azalea lace bug infestation!! Control can be done any time but best to time for when plants are not exposed to full sun - i.e., early morning or late evening or on an overcast day. Azalea lace bug control. I tend to lean to Neem oil for this sort of problem - very effective and a natural control.

Looks like some type of insect damage. It doesn't look like you have the tree in full sun, which it needs. It also may be getting pot bound. BT is not a variety I would recommend growing in a pot. It will do much better in the ground