Adding those nodes was not enough. The wallet tried to reorganize 500 blocks, but that didn't fix things.

I fixed my wallet in the end by following these steps:

1) Close the wallet

2) BACKUP (at least wallet.dat)

3) Remove all config/blockchain files EXCEPT wallet.dat and ColossusCoinXT.conf.

4) Then in ColossusCoinXT.conf replace all old addnodes with these 'clean' ones (although I could only connect to the first 2):

addnode=82.211.30.118:51572
addnode=84.200.16.124:51572
addnode=35.203.147.109:51572
addnode=35.199.165.239:51572

5) Start the wallet and synchronize.

At least my missing SOPool mining payments appeared. Thanks.