[Tilted Irish Kilt]

EternalVigilance :" There are still dozens of watermelons that just don’t seem to want to ripen though..."

Consider putting the almost ripe fruit, elevated off the ground on top of any large cans in the garden.
Frequently , overnight cold ground will chill the fruit , thus slowing down the ripening; use whatever heat you can get this late in the season.

[EternalVigilance]

I hear you. Sounds like a good idea. However, it’s remained quite warm here so far. I think it’s just the variety. The black diamonds ripened weeks ago.