HELP! Magnesium Deficiency?

[buds73]

Hi all, I went to water my plants and to give them a check over earlier and came across a couple of lower leaves on one of my plants with some yellowing on them. I think it's a magnesium deficiency but thought i would just check here to be sure. I normally give my plants a once over each day to check for problems however i didn't get the time to do this yesterday before lights off but checked the day before and didn't see any yellowing then so it's something that has come on in the last 24-48hrs. Pics below of 3 of the 5 leaves i found it on. In hindsight i should have left them on to see if the problem gets worse but found that out after i removed them.

[CaptainWiese91]

First of all.
did you check ph in soil or you’re medium ? Not only the water but also the medium ?
I would start with a ph check first.
how big is the pots and how much water are you feeding the plant ? + how old is the plant and how big ?

[buds73]

I have used a 3 in 1 prong meter to test soil so can't be 100% accurate but its showing roughly 6.8. The soil ph did rise to just over 7 about a week and a half ago so i have been doing the ph on my water to around 6.3-6.5 to bring it down. Pot size is 3 gallon. Plant is 58/59 days old and gets about 750ml water every 2 to 3 days and when pot is light. I only add nutes (Bio bizz grow) every other watering at a quarter dose any more than that strength and i find i start to get nute burn at the very tips of my leaves. Plant is just over 12 inches, roughly 30cm tall and about 16", roughly 40cm wide (but in an oval sort of way).
Plant is currently on its 5th period of 12hrs dark but i've not added any bloom nutes yet, was going to give them their first dose earlier when i watered but held off when i saw the yellowing leaves. I should add that i don't use any calmag as i didn't think i was going to need it.

[CaptainWiese91]

5 period of 12/12 ? Is that week 5 of bloom ? Or day 5 ?
So you are not adding any cal mag supplements?
your Ph is fine. I would have done the same.
3 gallon pot is 11 liter, roughly. It’s a fine amount, I don’t think either it’s your watering practice. I have 30 L pots and only give them 1,7-2.0 liter max every time.

what kind of bloom Nutes? Also bio biz? Or a bloom booster without N in it ?

[CaptainWiese91]

Buy some cal mag and give it some in every 2 waterings 👍🏻

[buds73]

Thanks for your replies.
Day 5 of bloom i meant. My pot is actually 12 litres i rounded it up to gallons lol.
Bloom nutes will be Bio Biz bloom NPK is 2-7-4. Bio Bizz Grow NPK is 4-3-6
I'll get some Calmag tomorrow and try that, i should be able to source it locally.

[CaptainWiese91]

Don’t feed it more veg nutes looks like it have enough of the nutrients it needs.
I grow in soil too, but from day 1 I have cal mag in my spray bottle and have almost cal mag in every other feeding to be honest.

[buds73]

Ok thanks i'll lay of the veg nutes and give them some Cal mag on their next watering. You say you have calmag in a spray bottle, can that be sprayed directly onto the leaves? My tap water ph here is quite high so didn't think i would need the calmag. Did download a data sheet for the water in my area but if i am honest i don't know whether its good or bad lol.

[CaptainWiese91]

No I spray the soil. I germinate I the final pot. So the first 3-4 weeks I use a spray bottle to water the plants.
I never to foliar spray with nutrients or supplements. I honestly think it’s useless.
I mix 10 ML cal mag in a 6 liter water bottle. And I always used my tap water. Just using citric acid to lower the PH

[buds73]

Ahh right i see. I only used spray for first couple weeks with just water not used spray since.