You have correctly identified Channels 13, 14, 21, 22, 23, 24 as having issues but it's not the power levels, all of which are within specification, it is the Signal-to-noise levels that are below the 34.5 db threshold that is the issue. In other words you have a lot of noise on the line and you will need an engineer's visit to look into that.
@TheGiraffe wrote: Thanks for fast response. Are they the SNR values? What could cause noise now if it was okay a few days ago?
I'll book in an engineer
Yes, the downstream SNR levels should be greater than 34.5 db. I should also have mentioned that whilst still within specification (less than 51dbmv) your Upstream power levels are at the high end of the scale and that together with all 4 Upstream channels being on 16 rather than 64 QAM would also suggest a noisy connection.
Check the security of the cable connections at the back of the hub and the wall socket and if they are tight then you've done all you can and an engineer will be needed.
Changes like this can be due to numerous reasons so I won't speculate.