Or ! You could be really creative.
1- Create network tags for your WAN speeds. Eg : Network 1 : TAGS : ['Wan1-100-100',Wan2-50-50'] That would indicate Wan 1 Speed of 100Mbps Up and 100Mbps Down. Same for Wan2.
2- Insight -> Alerts -> Create an alert for EVERY single WAN Speeds by selecting the appropriate network tag :
If you only have 2-3 ISP with 1-2 speeds , that can be done easily. Otherwise it's hard to manage and maintain.