Use the tap water. That ph should counteract the acid in the soil. Those size of plants, depending on how much fish liquid is in the soil. Shouldn't need more nutes for two weeks. A solid 14 days. Some of the nitrogen in the fish fertilizer is slow release. Other ingredients are quickly absorbed. The plants need to use what's already in the soil and their root system isn't that big yet.
One thing about cannabis is it'll clean the soil. But the PH has to right. 6.5-7.0. If not, they'll continue to struggle.