I'm going to assume you meant fast pass as spirit stones hasn't been a thing for months. And yes this is normal, they have an expiry of one week (7 days), in the run of a week you can build up around 20 to 24 fp, but it is also around this point that your start of week fp start to expire.
Typically at 3 per day by Sunday you should have around 21 to 22 if you also haven't bought any with points or used them. On day 8, your first three fp expire, but you replace them with a fresh 3. So on for the following days.
Now this cap can be broken by waiting till later in the day to get your first 3 fp then on day 8 get your daily fp early... of course later that day 3 fp will still expire.
Also the cap can be expanded when you use points to buy fast passes.