FBM UPS rates shot up/discount gone

I know another seller posted this question already but I really need answers as this has been an ongoing issue for the last month and it’s hurting our business. My partner and I have been doing Amazon FBM since February. We’ve done amazing since we started, enough to both quit our jobs and do this full time. We went on vacation last month for a few weeks and when we came back, we saw that the overall USPS & UPS rates (which are the the two carriers we primarily use) have skyrocketed. At the same time, the UPS discount also decreased from 75% off to maybe 25% as of last week, now it’s even lower to about 10% this week.

Does anyone know what’s causing this? We cannot continue to ship product anymore at these rates, and like I said this is our only form of income.

Also, no we do not have any other carrier account connected to our Amazon seller account, which was the only suggestion seller help gave us.