I would only consider the use of d-etuning reactors if the bere is sufficient harmonic voltage present to drive harmonic currents through the capacitors.
This can easily be proven by measuring the total current into the capacitors. If the current is 10% or more than the correct current for the capacitance and voltage, then you do have harmonic voltages and harmonic currents and de-tuning reactors should be fitted.
Before you fit de-tuning reactors, you need to ensure that the capacitors are designed to be used with de-tuning reactors. De-tuning reactors and harmonic voltages cause the voltage across the capacitors to increase and while the KVAR rating may be based on a supply voltage of say 415 volt, the continuous voltage rating of the capacitors needs to be in the order of 525 - 600 volts for a 400 Volt installation.
De-tuning reactors increase the costs and also the losses in the correction system. This results in a considerable increase in the heat to dissipate from the enclosure.
First, determine if there are harmonic currents flowing in the capacitors by measuring the capacitor current.
Second, if the currents are too high, then determine if the capacitors are rated for use with de-tuning capacitors. If not, you need to replace the capacitors with capacitors suitable for use with de-tuning reactors.