Diff 409 is not compatible with whole network hashrate..
This is what is going wrong :
The coin is broken. Without KGW in place, it has at re-target of 1 block. The 1 block re-target non KGW is very flawed. If you get lucky and get a coin really quickly it will whammy you with what we have right now which is 25 min between blocks. Once the next block gets found (during the 25 min window) it will set the difficulty really low to make up for the last block. Then that one gets picked up too quickly and back we are again at the 25 min re-target.
Each pool depending on if they found a block recently will change their estimates on how many coins you can mine in a day. If they found one recently you have a higher rate, if you haven't you get a lower rate.
All simple calculations. The coin will need a fork to change the 1 target to at least 10 until KGW is implemented