Rockwool slab users

[Roadblock]

Hello guys , had a mate give me some new slabs the large 300ml wide ones , well anyway I cut a corner and now paying for it , I ran the drippers for 6 hrs prior to sitting cube on top , I know I should have washed them out properly , well the plants went great guns and are 2wks in and 18inchs high and round and have been turned in to flower for 4 days , then all of a sudden I got bright yellow at all new growth sites , I peeled the plastic wrapper back and much of the big slabs is quite dry so I flushed the entire slab thoroughly with solution by hose and now Im waiting , the res PH has been kept at 5.8 all along and drawing samples out of now washed slabs is 6.0 anywhere in the slab , I think they just spiked by the unwashed rockwool as they got a bigger root system , I have others in perlite in another spot on same nutes and water with no such problems .

 

My questions , will they get worse before they get better and will it cause permanent damage , will there be a big hit on the plants over all because they are in flower ,,,, they are nice and turgid and look good except for the bright yellow tips and a little bit of leaf twist , hope someone has had similar probs in slabs and can put my mind at ease as to whats gunna happen .

 

Thanks Rod

[sunnycoaststoner]

dude its sounds a little like nute burn with yellowing tips, i grow in rock wool all the time and 6 is nothing bad. 5.8 to me sounds a little low any way, mine is between 6.0 and 6.5 all the time and my plants all grow into awsome trees in no time. just prune thee yellow stuff away and wait and see what happens. what ec are your nutes running at ? besides the yellow they sound happy enough. they will show/tell you when the not feeling well. happy growing.....

[Roadblock]

Thanks mate , nah its not nute burn which is running at 1.6 CF and dumped weekly and my flow is quite high Im very diligent with my values ,, when I say tips I dont mean leaf tips I mean the centre of the crowns , you know the centre of the growing shoots , the newest growth , cant cut them out ,, Im thinking the dry unwashed rockwool would have been very high PH as it picked up moisture from the drippers while the nutes channeling through would have been the same as the res thats why I never picked it up in res which was stable only rising about .2 daily , but as the plants grew and sent out roots they would have hit the mostly dry unwashed wool , thats my theory , these plants powered early and like I said I have another room in perlite that are perfect and on the same everything except the slabs , Ive never had this before , but when ever I used slabs before I washed them real good first .

 

I,ll post some pics tomorrow if nobody chimes in .

 

Thanks Rod

[sunnycoaststoner]

oh ok, i had a similar thing happen once and came to the conclusion that it was bud rot caused by too high humidity and hot lights. humidity was around 70/80% during flower, should have been around 40/50% and funnily enough the mould followed as well. a fan speed controller helped me control the humidity, but damn i lost a lot of great buds from it.

 

oh yeah some pics would be great cause can only guess and throw ideas at ya till we see it for ourselves.

[Roadblock]

They seem to be growing ok and fast its just the yellow that came into the crowns basicly overnight , the photos dont really show what Im seeing because of the white balance of the images , I should have shot them in raw mode instead of jpeg , the two close up tips you can see it , the pic of the the full plant is a White Rhino and although it has the same problem its not as much as the other strain , I really think it is was a PH problem that caused it , but Ive never had a PH problem before so Im not really sure , Ive flushed them out and my values are right so I spose there is not much else I can do except wait and see , they are only 2 1/2 weeks out of the clone box and have been just turned into flower a few days , the temps are 27cel lights on and 20cel lights off , humidity is 50% , its perfect time of year here now .