We definitely need more information to help you, but we would be glad to do so :) A couple of pictures that aren't from a birds eye view might help as well.

Thank you all for the responses. My long winded post is just an attempt to give you broader picture.

I'll add more details like exact variety and more pictures by tomorrow morning.

I don't know about about pH values of my soil, but general observation is almost every neighbor has a lemon tree and those are thriving. I do realize this does not answer the exact question, but knowing my neighbors, they almost don't take any care of of the trees except occasional pruning. They don't even water the trees except theirs are established mature trees.

My naive question is can pH values change that much from next door. I am in Fremont/San Francisco bay area and our lots are typical small lots common in this housing crunched market. So I doubt if there is significant pH change between next door and my lot.

I started noticing the change in the plant (lack of new growth) during early part of the year. We had lot of cold weather and rains this year. I did some searches at that point and attributed it to weather and damp soil as I read at many places that these trees don't like too much water. After weather improved, my neighbors trees also improved, but mine started from going from bad to worst and started loosing it's limited number of leaves.

Water is standard city water, we don't have water softener and don't believe we need it.

So far, I have fed the plant twice in last 4 months, one table spoon of miracle grow. When I dug the hole for the plant, area was mixed with home grown vermicompost.

So, the most obvious culprit is the Miracle Gro.... lose that and get a good citrus fertilizer; and that will go a long way to fixing most of your problem. Your question, can soil change so much from one property to another??... possible; but in your neighborhood, NO.

First, that is a pretty small tree to plant in the ground. How large did you dig the hole in relation to the dementions of the root zone? When planting a citrus tree in the ground, always refill the hole using only the dirt that was removed in the digging. Do not add any amendments. Normally, when a citrus tree is planted in the soil, and it drops all or most of the leaves the problem is normally with the roots. I don't think Miracle Grow fertilizer was a problem, unless you applied to much fertilizer and burnt the root system. If the soil the tree was planted in has slower drainage, digging too large of a hole for the size of the tree, creates a lake every time you water, which is VERY detrimental to the root system.

You've got it planted with mulch. Most likely your problem is root rot. I would recommend that you take the root ball out of the container and examine the root system. If you see black root tips (where it looks like the anchor root has completely rotted off except for the tip which is black) or darkened feeder roots that have detached from the root system that's an indicator that it is root rot.

If this is the case you'll have to treat it. Clean off all of the rotting roots, clip off all of the blackened root tips and wash off any soil from the roots with garden hose. Next, make a solution of 20% chlorine bleach and 80% water put it in a bucket deep enough to to contain the entire root ball for 15-20 minutes. Rinse off the root system with water and replant in different soil. It's very important that you do not use the same soil because root rot is a type of fungus and can persist in the soil for long periods of time and simply re-infect your roots if you put it in the same soil. Chances are it isn't root rot but if it is, I hope this guide helps.