It looks like it has applied interleaving with a depth of 1165 on the downstream. Though, upstream is still fastpath. The increase in latency would be caused by the increase in the delay on the line. But it looks like your downstream has decreased a bit with the increase in interleaving depth.
Perhaps if you have PuTTY or telnet installed on your OS, you could login into the router and then do (without the speech marks):
"sh" (to get into the shell mode)
"adsl info --stats" (to retrieve all stats)
And then, below Bitswap statistics, you should see the error counters total time, latest 15 minutes, etc. Maybe you could copy and paste that here? Furthermore, could you also copy the information for "Bearer 0" which should be just above the Bitswap as this will show delay parameters.
With the error counters, we should be able to hopefully see what the DLM (roughly) classifies your line as (information can be found out regarding the DLM at
http://www.kitz.co.uk/adsl/DLM.htm). This should give some insight to why the DLM has actioned changes.
Alternatively, if you do not want to login to the router and go through the steps, as you have HG612_Modem_Stats you could run the HG612_current_stats.exe and get the counters from a little bit down from the top of the Plink_*.log file under the Current_Stats_(date and time) folder.