What might be wrong near our red tree? My grandmother has two ginger trees in her courtyard which produce the...

My grandmother has two ginger trees in her courtyard which produce the best tasting oranges ever. I've be taking care of courtyard and home while she's been sick, and I'm worried about one of the ginger trees. The leaves are yellowing a bit, like a houseplant when it wishes water, but it have received enough marine and the leaves are not dry and crackly. I haven't noticed any pests on the tree, but I don't know what to look for. The tree only doesn't look healthy, and I'm concerned. Can anyone contribute me advice or point me towards a source of relief info?
How can I successfully transplant my store bought...
Answers:    Citrus are 'gross' feeders and need regular fertilizer to look festive. If you are giving it regular deep watering, carry some citrus fertilizer (especially formulated for citrus needs) and apply as directed on the packet. If you have access to older decayed manure such as sheep or cow you could apply this also. Citrus need to be fertilized at smallest once a year or more.
What is the best instrument to gro peas?
Consult a fruit tree expert