Hi I'm new on here and need a bit of help. i have a few plants some of which have brown spots and the tips get crispy. They are in a potting/cutting soil, perlite and vermiculite mix and am feeding them with biobizz. They are about 5 weeks old and are clones. Only giving 2ml nutes per 1litre which is half of what it says on the bottle. just got a ph test kit and the water and nute mix seems to be fine, well it is around the 6 mark, which from what i've read seems healthy enough. My test kit only tests between 6 and 7.5 as i wanted one quick so got one from the pet shop for aquariums. I don't have a soil tester though so don't know if thats ok, but its not affecting all the plants. I also have some seedlings in rockwool that are about 3-4 weeks old and they seem to be doing just fine, although they're getting diff nutes but ph is fine there too.
I have done a few grows which have been successful and didn't really have any probs till now. I have read a few things and sites about deficiencies and ph probs but can't really find one that matches my prob. On one site it looked like a calcium def caused by ph prob but since ph seems ok could it still be calcium def? I water when they need it, around every 2-3 days with nutes, could i be over nuting them even though the other plants are ok? the plants also seem to be slowing in growth, 2 or 3 of them are getting these spots quite bad and the leaves are looking well crispy.
Does anyone have any ideas on what i could try? thought about flushing them but i'm a bit dubious incase they get over wet if you know what i mean, how would i go about it properly? i haven't needed to flush before.
Also, do you need a soil ph tester to test the soil ph or does the runoff give an accurate enough reading? and if so how do you correct it if it is off? Sorry if this is a bit of a babble but don't want to lost my babies and getting desperate!!
I will try to get pics on tomorrow as i only have a cam on my phone and it needs charged the now.
Please let me know if you need more info to help me, thanks: