Responsa על ראש השנה 3:16

You asked about a community that wished to declare a fast on Monday, Thursday and Monday, and the first fast day fell on Tu Bishvat. Should they be concerned and postpone the fast to the following week or not? Thus my inclination is that the fast should be postponed to the following week, and the fast should not be set because we do not find any fast on Rosh Hashanah.