Some lower trapezius isometric holds as an activation drill would help them develop a mind-muscle connection for their lower traps. It’s very likely they are underactive and lengthened with over active traps. Excessive trap stretching is also in order! Also, make sure the client is doing their latissimus training correctly. 90% of the time they don’t maintain the healthy arch in their back during lat pull downs, which helps to recruit the lower traps. An improperly developed back will completely halt their functional strength in pressing movements as well.