Please help in diagnosing problems!

[electromagnets]

Hey everyone,

New grower, new member. First off thanks for the wealth of information here! It’s been super exciting to find such a comprehensive forum dedicated to autos with such enthusiastic and knowledgeable members!

So here’s my situation: I’ve been growing autos on my balcony all summer, started with 2 Royal Haze autos from Royal Queen seeds, and brought them from seed to harvest outside in the summer sun. Thanks to this site and a few YouTube growers like Bill Ward, I quickly got deep into learning how to train the plants, using nutrients, etc etc. In other words, being jobless thanks to covid, I had plenty of time to dive in head first into the world of cannabis cultivation.

So now I’ve got 7 more plants going but the weather is changing where I live, and I realized that I want to continue to grow year-round, not only in the summertime. Problem is that my flat is quite small (no space for a full-on grow tent), but since I was redoing my kitchen anyway, decided to build in a ‘hidden’ grow box under the kitchen countertop that measures 120cm (4ft) long, 60cm (2ft) deep, and 100cm (40in) tall. I bought one of the new Migro Aray 240W lights, and for now painted the inside of the box with flat white latex paint that I already had. Will eventually upgrade to silver diamond Mylar. Initially I had an exhaust fan rated at 135qm per hour but recently upgraded to a much stronger one that I was able to borrow from a friend, to see if it helped at all with my heat issue.

I’ve currently got 3 plants inside the box - 2 Royal Haze Autos and 1 Northern Light Auto, all from Royal Queen. They’re all in week 11 at the moment, and lived their entire lives outside on the balcony until putting them in the grow box 2 weeks ago.

One of the plants is right on track to harvest at 12 weeks, while the other 2 are lagging behind (also had this with the first 2 plants I grew entirely on the balcony - 1 of them took 17 weeks to finish!).

Anyway so the situation now, is that not only are the leaves yellowing, but also developing brown spots (photos attached) And becoming very brittle. It’s happening the worst with the plant that’s furthest into flowering, but also started to happen to the other 2 as well. Additionally as you can see, some of the leaves are drooping quite a bit on 2 of the plants, even though I’m sure I haven’t been overwatering them. They’re all in light mix soil from biobizz, and I’ve been using General Hydroponics tri-part from the beginning, adjusting the balance based on the life cycle of the plants and using nutrients in about every other watering.

I have had a small issue with powdery mildew, but have been able to keep it under control by just wiping it off of the leaves diligently and spraying neem once per week. In a few cases where I found it on buds, I cleaned it off using a neem-soaked Q-tip.

I’ve also got some thrips merrily living in there, but again using neem and killing the larvae when I see them has kept that from becoming anything to worry about either.

The main thing though, is that until recently the temperature inside the box was at a pretty steady 30 - 31 degrees Celsius, which is way too hot from what I understand. As mentioned above, to remedy this I found a much stronger ventilation fan to attach to the carbon filter, and now the temp is steady at 25-27 Celsius, ~45% RH, but the leaf yellowing / brown spot problem doesn’t seem to be subsiding.

So there it is, in a nutshell. If I’ve left out any key info, just let me know and I’ll add it to the post - otherwise, have a look at the photos and PLEASE HELP!

Thank you!!

 

[Mañ'O'Green]

@electromagnetsWelcome to AFN

Since the nutrition levels you use did not cause problems when outdoors. I am going to look at your environment as the problem. When it was too hot it was probably also too low in humidity. If the RH gets out of range high or low the stomata (breathing holes) in the leaves close to retain the moisture in the leaf. When the stomata are closed the plant stops respiring. Water stops moving up through the plant and it no longer transports the needed elements for growth. This causes a nutrient deficiency even though there is plenty in the root zone the plant simply cannot take it in. Then most new growers see the indications and add more elements to the soil that now causes an excess nutrient lock-out. Get your environment right 68°F/20°C night 78°/26°C Day RH 40%-60% The damaged leaves will not recover.

If you are getting PM you do not have enough air-flow in, around and out of the grow space. I would use Southern AG Garden Friendly Fungicide for your Powdery Mildew.



Orca Grow Film is better than Mylar.

Cabinet growing is a learned skill.

 

[electromagnets]

Thanks Man’o’green!

Actually, the humidity in the box has always been between 40 and 50% RH - I’ve got a small travel humidifier that pumps out the perfect amount for the size box / strength of ventilation fan I’m using.

My only (inexperienced but researched) thought is that it could be light burn - does this seem possible to you? For the first 9 weeks the plants lived outside with only a few hours per day of direct sunlight, the rest indirect / overcast. I live on the top floor with a WNW facing, uncovered balcony, but we haven’t had the greatest weather this year sadly. When I first put them in the box I pumped the Migro Aray up all the way and put them on a 20/4 schedule. The light is hanging about 18cm from the highest point of the canopy (Migro recommends hanging it at 16cm).

Perhaps it would be a good idea to dim the light a bit, and raise it a little further from the canopy?

Additionally, the plants seem to want a lot more water now, and I’m being careful not to over-nutrient them (and also simply flushing the plant furthest into flowering). Adding nutes every other watering, watering every 2-3 days right now.

Also re: powdery mildew, they got it from my cucumber plants while outside I live in Europe so I’ll try to track down that product you mentioned to fight it.

And lastly, what about the drooping leaves as well? They look overwatered in my opinion, and it seems like perhaps a separate problem than the burned / brown spotted leaves...

Would it help if I post more pictures of each problem separately? Any other info I can share that would be useful?

Thanks again!