Yes, so shall i write a proper letter explaining why i missed it in the first place and now when i have noticed so i am updating this section.Firstly rejection of visit visa has nothing to do with Spousal application ..
secondly you can write an explanation letter to case officer which should be convincing about missing that section unintentionally.. m sure they will consider it.
All the best
Do you think, it will be a negative impact on them on my application.