Growing wheatgrass in easygreen

Newbie here. I read in this forum that a wheatgrass can grow to 9 inches tall. The problem I have is that by using easygreen sprouter, I can grow my wheatgrass to maximum height of 5.5 inches. This is because of the limitation of growing container. I lived in a tropical country where the temperature runs between 30 to 38 Celsius (86 to 100 Fahrenheit). I want my wheatgrass to grow to 8 to 9 inchess tall. Can anybody help me on what to do?

Thank you.