According to flightradar24...
B-18210 did not fly the past week.
B-18211 flown TPE-BKK the past week on 2/29.
B-18212 did not fly the past week.
B-18215 did not fly the past week.
744 was scheduled to retire 2021/2022 but a recent cabin seating cooperation deal with AIDC was released so it's likely the 744 will continue to serve on China Airlines if current seats are replaced.
It's likely no 744s will be in operation for China Airlines in March and April. This could well be extended beyond due to the continue spread of corona virus.