Having the TBB and f8lure monitors running simultaneously shouldn't skew each others results.
Wrt yellow spikes on TBB monitor, it seems they aren't reflected on the f8lure monitor? If
the TBB monitor is incorrect then by the same token the TBB speedtester could also be giving you incorrect single thread speedtest results. Hence why i recommended f8lure to get an independent check on your TBB BQM, but it appears one monitor is telling you porkies...I would leave both BQMs running for a week or so and then do a comparison. Ideally you shouldn't have any spikes when your connection is idle.
TalkTalk Business 80/20
Netgear R9000 X10 running OpenWRT
My Broadband Quality Monitor