Whoa, I never expected this many replies so fast. Thank you every one. When you are using the stick to test moisture, do you let it "soak" in the soil or just dip it in then immediately pull it out? Thanks for the advice on the soil mixes too. Since I have three plants coming, I think I'll try each mix on separate plants. Maybe I'll be able to spot which mix works best for me before losing any of them. As for my growing environment... The soil I used for the first citrus was Miracle Grow Cactus and Citrus mix. Since I was afraid of causing more harm than good with the last two, I just left them in the pot they shipped in. I have no idea what soil they shipped with, but it sure looked like the same mix - just without plant food. The actual orange branch on all three plants was maybe 2-4 inches long. However, the rootstock on the last two was around 6 inches tall. With the plants nowhere near fruit bearing size, I figured I didn't need to worry about fertilizing just yet. I'm sure most of you would cringe at my grow lights. They are just a few 13W "energy efficient" full spectrum bulbs - the kind used in modern home lighting to treat SADS - jury rigged to a timer. It seems to work though. I have been able to grow opunta cactii, coffee, allspice, and vanilla among other things. For my smaller plants that need more humidity, I just place the bulbs at the top of my terrarium and use the timer to dial in the amount of light required. I don't have a humidity gauge, so I can't provide specific measurements, but I try to maintain my terrarium at a humidity similar to the feel of a local summer day. I haven't been able to confirm this with any records, but if I recall correctly, our summers are usually at 50-60% - maybe as high as 70%. I keep the temperature at 65 to 75 deg F in the winter. In the summer, temperatures might spike to 90 or 95 deg F. I've not had so much trouble learning to care for my other plants because I always had more of a grace period to figure out what I was doing. With the citrus, it goes from healthy to dead in the space of a week and I never have enough time to observe the results of whatever change I try to make.

I called a tree trimmer/cert arborist today. Murray's tree service-- in case any of you have used prior. He's supposed to come out on Thurs. to take a look and give me an estimate on trimming the oak. He said that it does indeed sound like the fungal problem that is going around Pinellas and Hillsborough currently. He said that professional growers have lost a lot of trees to it this year. It is an airborne fungus and highly contagious and will kill your tree and also spread to others. Definitely not good news. Today, I noticed my orange tree now has the same symptoms. He also recommended the copper fungicide as well, which I will definitely try (have not found any YET...at least at Lowes). But he said that it has not provided much to prevent the ultimate decline of the tree. I'm going to wait to see what he says further once he gets here on Thursday and will try the copper stuff. I'm not one to cut down a tree unless it is actually dead or close to it. While it is still bearing fruit and has leaves, it can stay in my yard. I am hoping for a miracle.... :(

I was looking at the very edge of the leaf, it looks like a margin along the outer edge. If that turns yellow and looks a bit burnt, that would look like fertilizer burn. All in all the plant looks great , I wonder if it came out of a shade house and is now in full sun, perhaps a bit of acclimatisation required. Make sure it gets a good watering where the water is washed out the bottom of the pot every now and then, just to flush any buildup out.

The pH of 7 is not a problem (any pH meter that cost less than $100 is actually worthless). The tree being in the same container now going on 2 years is not good. Have you ever pulled the tree from the container and examined to see if the tree is root bound with circling roots? They probably are. A citrus tree should be repotted every 1 to 2 years? A root bound tree equals problems plus no, or not much growth, and eventually death.Organic Fruit & Citrus Fertilizer (3-5-5) is simply NOT a good fertilizer for your container trees. Organic fertilizers are "OK" for outdoor in ground trees, but do not work well in containers due to the low levels of microbes needed to make the nutrients available to the tree. Fertilize your tree a MINIMUM of once month.The leaf you show in your photo is definitely NOT a magnesium deficiency. I believe it is just an old leaf that has out lived it life. Good luck to this tree's future..