Almost every afternoon, Internet speed crashes around the same time.

Almost every afternoon, Internet speed crashes around the same time. I have 150mbs, and speed drops dramatically. And it self-resolves after a half hour or so.
We have several items connected, mostly IOT, not using much bandwidth.
Talked to Tech Support in Jamaica, all they could say was that 150 mbs was not enough bandwidth and I should buy more.
Anyone else having this issue?