Bubbly but no rise starter

Help!
We are on day 18 of our sour dough journey I had a false rise on day 2/3 it was a great rise! It is super bubbly but only rises about 1/4 never doubles in size currently feeding it 1:1:1 ratio with spring water and Edmonds high grade flour
It’s kept in the oven with the light on as our house is on the colder side
Feed this morning at 7.30am photo attached below of the rise at 3:45pm
Any advice would be greatly appreciated!

@7.30pm stir it down instead of feeding. See how much it rises again. Then feed again before bed.

Your container is flared, so that is probably pretty close to double.