Fermenting fruit

So I made this beer with basically the recipe I stated, only I fermented with the German ale first, then racked onto the fruit in secondary and left it for about a month... over the course of drinking them for the past couple of weeks I’ve noticed that some are noticeably more tart than others... so tonight I took one of the first ones that got bottled and one of the last ones to get bottled and tried them side by side and the first one was perfectly tart and the second had almost nonexistent sourness... how is this possible?