There's no such thing... There are FRAs that trade in each ccy, but they trade independently.
When you trade FX fwds (aka FX swaps), you will be trading a forward exchange rate. That rate is driven by the interest rate parity relationship. That is what the OP is referring to and that's not really related to FRAs. Sometimes people use the term "forward points" or just "forwards".
So, in answer to the original question, the fwd can decline not just because of the spot moving, but also because the pricing of the expected relative interest rates in the market has changed. For instance, you could see this occurring recently in EURDKK.