Node runs for 4 weeks but reduces era.

report phala
I have 4 node running for 4 week but reduced era.
Fullnode name:
Lea_Pan02 | 5FjWY1d1ovaSxX8QuCmRdSfyy5e7Jdz1qS8DqzfH8jpQ21ui (Happen 18.08)
Lea_Pan03 | 5FHBXdAeRZYmiWj8mABqTd8PBWTwMqhmQ7n63x7Dk553hjo9 (Happen 18.08)
Lea_Pan06 | 5DCRSHcutiugEK878hdkHrEZXRFB2zNKQ54S5J3izUqEmXAK (Happen 15.08)
Lea_Pan07 | 5Ec2ygBtAdU5Bj7HJKodnJUEmYJXWNU1iBsKE1fc6SkpNeYG (Happen 18.08)
I have screenshot in 15.08(Lea_Pan02|96era,Lea_Pan03|93era,Lea_Pan06|53era,Lea_Pan07|92era) and 20.08(Lea_Pan02|87era,Lea_Pan03|55era,Lea_Pan06|74era,Lea_Pan07|70era)
Date: 18/8/2020
Environment: Testnet/Ubuntu 18.08