The cooler weather is causing what appears to be a beginning of a manganese deficiency; aside from that, expect some shock and leaf loss when you notably change the light conditions of a Meyer. Oh, yes... no, those leaves will not return to "normal"; the manganese deficient (IMHO) might well regreen with some mineral foliar or chelated MN application; but the important thing is the color of the new growth, when it happens. If the new growth has a brownish reddish color before turning to green, you will know you are adequately nourishing the tree. This post was edited by Johnmerr on Sun, Jul 20, 14 at 22:00

I very strongly doubt that your tree has a phosphorous deficiency. I have NEVER heard of a phosphorous deficiency in container citrus, when it is regularly fertilized with a NPK fertilizer. Phosphorous does not leach from a container, as does nitrogen and potassium. Nitrogen and potassium are both VERY water soluble and readily leach with every watering, but not phosphorus. All of the leaves that are turning yellow, and dropping are the older leaves on the tree. Your tree is withdrawing the nitrogen from the leaves (thus they are yellowing) to reuse in other part of the tree before discarding them. When a leaf no longer is capable of supplying its expected quota of energy to the tree, it is quickly discarded. There is no welfare program for citrus leaves. However, your tree is also under fed. If the tree's problem was other than aged leaves, you would be seeing yellow dropped leaves from the new leaves also. Also it is not wise to add this and that chemical in hopes of coming across a cure. First ascertain what the problem actually is then correct it. I'm sure it was also not helpful to the tree to let it remain in the same container and "soil" for 5 years. Fertilize the tree using a high nitrogen fertilizer. You can add vinegar if you wish, but there are much better ways to acidify. Organic acids such as vinegar, have an extremely short life.

Johnmerr, Thanks for your insight. I think you're right regarding the light issue. We live in the Seattle area and it's started to get cloudy and overcast these past two weeks. We were worried that the tree is not getting enough warmth and light. We were even considering to get an additional grow light last night! As you can see from the picture I just posted, the light is just an inch or two above the tree. Should we reduce to 1 light instead of turning on all 3 for the moment or leave them all off? The tree was transplanted into this current pot 1.5 months ago. It's supposed to be a self watering pot. I don't use it for that purpose but more for drainage. There are holes on the bottom of the inner pot and I've put some small pebbles on the bottom to facilitate drainage. The tree hasn't really grown any taller since we got it. It looks more like a bush than a tree at the moment. We were hesitate to prune it due to our inexperience. We were also not sure whether we should remove the fruits as well. There are 12 on the tree right now. Thanks for your advice, we will remove some fruits from the tree tonight.

What John said. I suspect too wet and you're seeing a proliferation of phytophthora, our bane here in San Diego county. Watering 3 times a week is a lot of water for us. You're probably better off while temps are cool to water deeply once a week. As temps rise, move to twice a week. Meanwhile, treat the soil root area with Agrifos. 2 Tablespoons in 5 gals of water. Treat once a month x 3 months. You don't mention what fertilizer you're using, but try to find a citrus fertilizer with a higher N to PK ratio (5:1:3 is the optimal ratio, but you'll never find that, so try to find something close to that), along with all the micronutrients. Fertilize 4 times a year from late early February through Oct/Nov. And, I would not let such a small tree bear so much fruit. Let your tree get established before it puts all of its energies into producing fruit. And CLM doesn't hit us until late June/early July through about October. It will only attack new tender growth. Careful with the Neem, as it burn tender new leaves if our temps go above 85 degrees. Patty S.