Pending time the investments are being made by the guardian, the guardian shall not be chargeable with interest; provided, that the guardian shall not be allowed more than four (4) months in which to make the investment. If the guardian does not make specified investments in or on the securities named in §34-5-114, the guardian shall be charged with the rate of interest, not exceeding six percent (6%) as the court in which the guardianship is pending may determine to be the fair value of the use of money at that time.