Canna flush

I wouldn't add anything else if I were you I would just flush with plain water ph'd to around 6.5 Its always a good idea to collect runoff and test its ec and ph. You usually find that the ec is stronger in the runoff because of lingering nutes from previous feeds and ph is often different too, if it is too strong then you either want to flush or use much lower feed next time. I like to alternate feeds, one with nutes then one without etc it helps avoid this issue. As for ph I change it every feed, I use coco but I'll give you an example using soil which I would aim to be around 6.5 throughout. If my previous feed runoff measured 6.0 then I would feed 7.0 this time, if my previous measured 7.0 then I would feed 6.0 this time, if my previous feed was 6.2 then this time I would feed 6.8 etc and so on hoping to land in the middle around 6.5. Hope this helps