I’m just gonna point to the unmentioned elephant in the room, regardless if it has any relation to your current issue, not because I judge anyone for it, but because I’ve myself had to learn this the hard way.
Switching a plant between in- and outdoor is asking for issues.
Indoor, the goal is to create an environment free of pests, because the indoor environment creates the perfect environment for these pests, and thus they will thrive and population blooms will follow in quick succession.
Outdoor, the goal is to create a balanced environment where, if pests are ubiquitous in presence, predators are usually also present to some extent and will provide some counterbalance, and we work towards having this healthy balance by providing attractive plants for the beneficials, and by adding beneficials themselves, among other things.
IF you are living in the US, currently there are a shitload more people growing outdoors then where I live, and honestly even where I live moving plants from out- to indoor is a budding disaster waiting to happen. The more plants that cater to cannabis pests (so cannabis and hemp plants) in a given region, the more you will see insects that are more than happy with your outdoor plants as a host.
Bring them in, and you get not just the insect you brought in, but the mites they may have brought in, and then they start an all-you-can-eat hot tub beach party right in your indoor grow room.
Here’s a really interesting picture of a whitefly carrying broad mites along, just for a visual proof of how these awful types of critters work:
(for size reference, broad mites, just like hemp russet mites, are nearly invisible with the naked eye)
I hope your room is still clean and you manage to keep it that way, regardless what you do with this information. Best of luck!
About the issues at hand.
You are using a SIP. That means salts can not flush out. Your symptoms don’t necessarily need to be a salt problem, but it can be.
The advice I read here to give it a proper flooding with the right nutrient strength and lots of run-off is the best I have seen yet. I don’t think it’s a pH issue. I do think heat will be part of the equation here so moving your lamps up or dimming them a bit if they have a dimmer function will probably help your plants as well.
What it looks like to me is you have a combination of a starting salt buildup and heat.
Excerpts from The Cannabis Encyclopedia (Jorge Cervantes):
…in excess of 50ppm, sodium is toxic and induces deficiencies of other nutrients, primarily potassium, calcium, and magnesium… …Very low levels of sodium appear to promote higher yields in cannabis.
…Sodium excess causes potassium deficiency, which in turn causes internal temperature of foliage to climb and protein cells to burn or degrade. Evaporation is normally highest on leaf edges, wich burn.
…Using too much baking soda as a fungicide can also create an excess.
And on Potassium deficiency itself (same book):
…Potassium deficiency causes the internal temperature of foliage to climb; beyond 104°F(40°C), it causes protein in cells to burn and degrade. To cool down, leaves evaporate moisture. Evaporation is normally highest on leaf edges, and that’s where the burning takes place. Up to 70 percent of a plant’s energy is “burned” to keep cool.
Potassium in excess also moves to these far areas, pores at the ends of the veins, and accumulates, causing this burn that is often confused with general salt burn but is not. The chlorosis must be seen first and a dulling in the cuticle layer of the leaf, all on older leaves.