By definition TSS is referred as soluble solids dissolved in a sample taken and most common soluble solid is sugar. In general the relation between TSS and sugars is quoted to be directly proportional.
In my personal observation and according to some published papers there was a variation in trend. It could be due to different maturity stages of fruit when picked, different storage conditions and other fruit and storage related parameters.
The organic acids in the most of fruits decrease at ripening stage due to conversion into sugars through the series of cycles in plants , hence their concentrations decrease on ripening.