Rates are dropping(yield) on buying debt(debt vehicles) which means they become more expensive. I am getting less for the same amount of cash put in. And it is currently a slow process. Short term
Well your short term reference was clear as mud.
You are correct when the yields on t-bills drop they do become more expensive. But it's an inverse relationship and what you are missing is what is driving those yields down! People are looking for a safe harbor and treasuries are the gold standard for that. The $6T that came out of stocks didn't just disappear. It went into short term and long term debt making them cheaper.
Look at your chart and compare it to how the market was doing last July. The market was cruising along but slowly started to slide when Trump was elected in November.
I got out of the market in January so I contributed to your problem I guess. I'm not getting the same returns I was in July but I'm not losing money either. You simply choose a different path last year and now you're not making as much money as you were. Join the club.