estaban enfriando
-they/you were cooling
Imperfecto progresivo para el sujeto ellos/ellas/ustedes del verbo enfriar.

enfriar

Es solo que los McNuggets se estaban enfriando.
It's just that the McNuggets were getting cold.
Solo dos de las tres bobinas del circuito se estaban enfriando.
Only two of the three coils in the loop were being cooled.
Palabra del día
el patinaje