Hi people I’m back with another (problem) question. Indoor grow with soil. The soil pH is 6.3 watering at 6.6 with a run off of 6.4. Temp between 78 and 60 degrees. I thought I had a magnesium deficiency problem, and treated it with Magnesium Chelate, at half the recommended dose, twice over two weeks. see attached photos. nothing changed. now some leaves are yellowing on the tips and on the edges and some turning completely yellow. I have tiny little fly type things flying around my grow space, I believe they are called fungus gnats. Is it possible that they could be causing these problems, and if so what can I do about it. I have put up some yellow sticky paper to trap them, and found a few stuck after just an hour. I don’t believe nute burn is the problem. I have switch the light ( TS 600 LED) 12/12 about a week ago. Not a lot of leaves have been effected< but would like to nip it in the bud…… before she really starts to flower. the gnats have been around for quite some time, but didn’t seem to be eating the plant, so I just squashed the ones I could get hold of. I’m getting a little stressed now because everything seems how it should be, except for the yellowing.
@Dillo. Have you checked your runoff to see what ph is.
And if you could. A pic of the plant overall would help too.
Oldguy the run off is 6.4, watering @ 6.6 soil pH is 6.3
It’s in a 250mm pot, about 6 gallons I’d say. I’ve been thinking it might be root bound. Is it too late to repot??
Fungus gnats can cause issues with roots if they’ve been around for awhile.
I’d want to get them under control before going the transplanting route. Gnat nix sprinkled over the soil would help. Sticky pads which I think you have will show you how many are still around.
Go ahead and remove those worst affected leaves to help keep any chance of mold forming.
Are those affected leaves getting any light or shaded.
Rest of the plant looks good.
And did you change anything in their feed recently ?
The only light they would be getting would be reflected light. I have only trapped around a dozen gnats in over 24 hours, doesn’t seem to be that many. The soil in the pot is not holding much water seems to run straight through. I used premium potting mix and now after research I think that was the wrong thing to do, maybe too much slow release nitrogen left in the soil. I did think the leaves were showing magnesium deficiency so I gave it some Magnesium Chelate mixed in the water, at less the half the rate recommended. also I fed her Sulphate of Potash at half the recommended. that’s all I have fed her in over a month.
Gotta get ready for work rt now but I’ll get back to you. 
Thanks mate almost bed time for me. 
@Dillo are you by any chance in Oz? Because a lot of what you’re explaining has been a problem for me also. I potted with premium potting mix and had exact discolouration of leaves and heaps of fungus gnats. Treated with a sprinkling of diatomaceous earth over the top soil over a week ago and they look much better. Still have fungus gnats zooming around, but no more leaf discolouration. If you have the same premium potting mix, I suspect it holds water - hence, the presence of gnats.
@Baz4 Yes mate I’m in OZ. I use Premium potting mix from Bunnings. it did hold water at first but now the water seems to run straight through. I have a Gold Leaf growing in another pot beside it, same soil but its still holding water. I don’t seem to have a lot of gnats at the moment, been holding the water back a bit. Where did you get the Diatomaceous earth from, ill have to give it a try. How far along is your grow, and what strain are you growing? the plant I’ve been having the leaf problems is a White Widow auto from ILGM but I’m pretty sure its a photo, its over 100 days old now and just starting to flower.
I thought so, because of your terminology… I had trouble accessing DE (diamotaceous earth) locally until I discovered it’s commonly sold at rural supply shops. Farmer’s feed it to their livestock.
I live in regional Oz, so our Bunnings doesn’t stock it. I’m growing mostly clones from bagseed,so genetics are unknown. Just bought some gorilla glue fem seeds from ILGM, but haven’t germinated them yet.
Okay mate, I’m in the big smoke.
Though I spend a lot of time in the New England area.
This is my first grow, still learning the ropes.
Anyway mate keep in touch. And happy growing…
No worries, mate. Will watch to see how you go.
@Baz4 Mate I was wondering what are you feeding your plants, and how much?
I’m not sure if I should give mine anything for a while…
I use a product called Flying Skull Nukem
@Shaneo420 thanks mate, I’ve got mine in a premium potting mix with slow release fertiliser, she is starting to flower. I’m thinking there might still be too much nitrogen left in the soil. Going to have to play it by sight, and see what happens…