Hi there Anythony,
The reward rate depends not just on how much liquidity you are providing, but also on how much others are providing at that moment. In liquidity pools fees are distributed among the liquidity providers, this is similar how the current initial liquidity mining pool works.
For example: you provided $1,000 liquidity and receive 0.001% of the pool rewards. The total amount of liquidity provided at the moment is $1,000,000.
If another $200,000 in liquidity were to be provided by other people, then the total liquidity pool would count $1,200,000. If volume didn’t go up and therefore fees didn’t go up, the same number of rewards would now need to be shared among $1,200,000 worth of liquidity providers instead of $1,000,000.
So, your % with your $1,000 would go down at that moment. If there were less liquidity provided in the pool, then your % would go up.
ETH Pools have seen mass increase in liquidity because of the UNI rewards - therefore your reward % has likely gone down.