If you feel that your starter has become weak or inactive, then I would suggest giving it a boost; don’t assume it’s dead, it’s usually not the case, so don’t throw it away, try giving it this boost and see what happens…
Across 48 hours, discard half then feed it 30g of your chosen flour + 30g water, each time, twice a day for the 2 days.
You should hopefully see quite a difference.
A note about flour, if you don’t already use a strong flour for your starter, I recommend trying one. It can make a massive difference to the activity of your starter.
Also, if your starter feels thin and when it’s active it only produces very small bubbles, feed it some flour only for the next feed. Stir in enough flour to really thicken your starter up then cover it again and leave it to work.
See how it feels and looks several hours later, hopefully it will be nice and active with good size bubbles like my Star in the photo at the top of this page.
Coming this year, Autumn 2020, my first ever book!