Whats wrong with this Key Lime plant

Bought from nursery , had terrible root rot due to continue rain , then i transferred to 9 inch pot , little larger the size of root ball .. plant started to recover , and started new grpwth of leaves , then after 3 months transferred to 5 gallon buckedt when it started root boubd in 9 inch pot ,, now the plant is losing those new leaves along with new growth but pale yellow color leaves ,. THE SOIL IS WELL DRAINED , NOT TOO WET ,, ENOUGH MOIST FROM INSIDE , NO UNDEREATER AND WATERING BUT STILL HAVING THIS PROBLEM