jkom has given you great advice. The Meyer looks great, well planted, no grass to compete, etc. I would recommend placing them on a drip system, since citrus do need a fair amount of water, especially in the hotter areas of the country. They also need well draining soil, which you probably have based on where you are. If planted in clay soils, they should be elevated, and the water well provided at the drip line lower than the tree crown. You may need to expand the wells as your trees grow, as you really want the water to pool in a circle around your tree at the drip line (edge of the canopy), as that's where your tree's feeder roots reside. Use a good fertilizer formulated for citrus, which will be higher in nitrogen and will contain micronutrients. You'll want to fertilize at regular intervals, and for you that should be February, May, and early October, but you can check with your local Master Gardeners for any additional timing for your specific area. It also would be beneficial for you to mulch your wells with compost or composted manure. That will do two things for your citrus: provide some water retention in your very arid climate, and also provide additional slow release nitrogen, both very helpful for growing citrus in arid climates on sandy or DG soils. I mulch my citrus at least once or twice a year with a small amount of chicken manure (very hot, so use sparingly), and then top with compost and wood chips as I'm on nearly pure DG, so very little organic material in my soil. For us here in S. California for the most part, iron deficiency is actually rarely an issue, as our soils have plenty of iron (but possibly jkom is in an area that is deficient - California is a gigantic state with some fairly wide differences in soil makeup). It is usually a manganese deficiency we see here, and that tends to be the same for AZ. I would check with your local Master Gardeners, again, though, to find out what your soil issues are, and fertilize accordingly. You can also use a micronutrient foliar spray too, which works very well if you notice your leaves getting pale or yellowish. Grow More Citrus Grower's Blend is a good micronutrient product. And do support your branches on your young trees, especially the Meyer, as Meyer's tend to be very prolific producers (my Meyer has no less than 50 to 100 fruit on it at any given time, I have Meyer lemons coming out my ears). Lastly, you are very fortunate to have quite a bit of online support for citrus in your state. I've included a link below, which also has additional links for you. Definitely check out Arizona Cooperative Extension's web site, it is a great resource for those growing citrus in AZ: http://extension.arizona.edu/maricopa/citrus-publications Your Master Gardeners are part of the University of Arizona Cooperative Extension, and are a great, great resource for home gardeners. Here's a link to your AZ Master Gardener manual: http://cals.arizona.edu/pubs/garden/mg/ Good luck, looks like you're off to a good start! Patty S. Here is a link that might be useful: AZ Citrus

To answer the original question it seems as tho the plants are just super stressed, and when they get stressed they drop their leaves and fruit to survive. They are getting much different conditions than they were at HD, where they outside or inside a greenhouse in HD? I am going to guess that they were inside or at least shaded, they had to be hardened off in before just putting them in full sun. This is done by SLOWLY introducing them to the sun for a short period of time gradually working up to full day sunlight. Stop fertilizing and watering until you know for sure they are dried out. Than completely soak and repeat the cycle. Citrus will survive slightly dehydrated better than they will flooded. The meter you are using measures the electric conductivity of the soil so if it is littered with fertilizers you will get false readings. Are you able to post pics of the trees and their pots? I would suggest a re-potting and pruning, but as you said you are new to gardening and this may scare you a bit. Do you have any friends with a green thumb that could help you with this? Don't expect any flowers or fruits till next year as said since the plants are so stressed, but you never know with some TLC and luck you may get some winter blooms. Again pics would really help, and good luck!

Then you probably have a root problem; if you water a Meyer too much it will drop its leaves; if you let it get too dry and then water it, it will also drop its leaves. I suspect you are overwatering it, being inside and cool. Check the temperature of the roots with an instant read cooking thermometer. Meyer roots will not grow if the soil temperature is 55F or lower; and if the roots aren't growing the plant doesn't need much water. Can you post a photo?

I have read most of these post...yet I still do not seem to see an answer for me...I have lemons, maybe a handful that have been growing for almost 10 months! and still are green as grass....Are they ripe? Can I eat them? Or do I need to just say "Hey, it will take a year and a half to get a yellow lemon?"..it is for sure a meyer lemon plant..*sigh* Oh I live in mid to north Georgia..Highs are low 90's and cools are 68ish..