It's possible your performance has actually improved. Bufferbloated networks have this peculiar characteristic that sometimes being faster makes you slower. If your ISP or drop box service has suddenly increased in performance, you may be pushing up against your max bandwidth, which can trigger many issues with bufferbloat, like high pings times and packetloss. Like kpa mentioned, give traffic shaping a try. Even something as simple as enabling Codel and setting your upload bandwidth may be enough. Very easy. It may be something else, but give the easy fixes a chance.