Looks like there was an increase in interleaving this morning; from 657 to 1377 on the downstream, and from 1 to 159 on the upstream. I can see that your delay is also 16 on the downstream and 8 on the upstream which has increased from 8 and 0 respectively, so essentially you have gained 16ms of delay on your line.
Even if you had "spare" SNRM, the application of interleaving or further increasing interleaving tends to take an overhead which may account for the loss of speed alongside possible other factors in relation to the line.
I can see that your ES on the upstream seems to be very high, with the last day in particular showing 657 ES in the 24 hours. This equates to an ES almost as little as every 120 seconds. I do not see anything outstanding other than this, but perhaps I have missed something or the DLM has just decided that your line is not stable enough. The DLM should work to the thresholds (
http://www.kitz.co.uk/adsl/DLM.htm), but unless there are some minor discrepancies in the logging then I am not too sure. But even still, I am guessing the DLM has acted based on the high amount of ES/SES on the upstream and enabled interleaving on the upstream (which added a delay).
Just out of interest, which modem are you using and which ISP are you on?