Possible calcium and/or phosphorus deficiency? Burn?

[mistertim]

I have 3 NL autos in 2x5 gallon and 1x2 gallon fabric pots that are about 2-3 weeks into flower (about 6 weeks in from sprout). They're in a 50/50 OF/HF soil mixture. Kind LED 600W light, I use distilled water and PH to around 6.5.

I've never added any additional nutes to my watering because the plants have been thriving just fine so far. I've actually been pretty surprised that the soil lasted them this long as I've read that it will usually last 4-5 weeks without any additions. I decided to start adding and go really slow, so all I added was 1 tablespoon per gallon of 0-.5-.7 Big Bloom (the bottle says 4 tablespoons).

I'm starting to see some browning on the tips of leaves and some dark blotches on some leaves. My initial reaction was nute burn but then I thought about how small the amount of BB I added was and it seems hard to believe that 1 tablespoon of a pretty mild nute mix would cause that.

So now I'm wondring if it's the opposite: the soil has run its course as far as what it can provide and I actually need to start adding more nutes. I'm thinking possible calcium and/or phosphorus deficiency from what I've read on here in other threads and stickies.

Here are the dark tips:

And here are the brown spots in other leaves:

Any help/suggestions would be greatly appreciated!

 

[5Lip]

I'm not an experienced grower in the slightest, but on my first grow the leaves looked almost identical to yours...I showed my local grow shop and he recommended cal/mag.....which I fed (half recommended dose) on my second grow and the issue never returned

 

[Heavily Medicated]

Timing would be about right for a P deficiency to show up, and P and Ca deficiencies can look pretty darn alike. I am not a soil guy.

 

[MrAutoGrower]

It’s been overfed with nitrogen by the looks of it. Signs of a lockout in there. Those spots tend to come out when people have been over feeding

 

[mistertim]

Thanks for the input, guys.

I figured I'd probably just need to test and see what happens, so yesterday I fed them with a 1/2 cal mag dose, 1/2 Big Bloom dose, and 1/4 Tiger Bloom dose and I haven't seen any ill effects at all thus far, so I'm leaning towards it likely being a deficiency as opposed to burn.

 

[MrAutoGrower]

Thanks for the input, guys.

I figured I'd probably just need to test and see what happens, so yesterday I fed them with a 1/2 cal mag dose, 1/2 Big Bloom dose, and 1/4 Tiger Bloom dose and I haven't seen any ill effects at all thus far, so I'm leaning towards it likely being a deficiency as opposed to burn.

U will notice further into flower if it is a burn. It won’t respond over night if it’s in soil. The tip of your leaves are burned, which is an indicator of over feeding. From there it will progress onto weird spots and stuff. If there isn’t a lockout in there somehow, then more P and K should fix it. But I have a feeling there will be a salt build up at the roots