Okay, Meyer lemons in containers are known to be difficult; change the light conditions notably they will drop leaves; let them get too dry and then water, they will lose their leaves; over water them, they will lose their leaves. Fortunately, if you continue to treat them well; and they have adequate drainage, they will recover. First thing is remove all the fruit; after that a little clean up pruning... prune any branches growing in a downward direction or crossing the center. If any branches turn brown/black, prune them back to the last live (green) bud. Don't fertilize until you start to see new growth; then feed them lightly until full recovery.