bad ph should I flush?

Ok so plants are a lil over 3 weeks have been giving distilled water with a ph of around 6. transplanted and added nutes yesterday (was looking a lil rough) I phed the nute water today and it was at like 5. Should I flush with right ph water?

thinking plants are a lil stressed from transplanting give it a few days then give it a light nute feed with 6.5 ph min