Japanese maples are know for the tips of the leaves browning as they are most tender and quickly will brown if conditions are right. Without knowing your soil type, watering 2X a week is likely too much. Roots need to be able to use soil air and too much water fills all the spaces in the soil, pushing the air out. Japanese maples favor an eastern or northern exposure in Northern Illinois. they can be planted in other locations if other trees or the home provide some shading.