When to flip to 12/12

A direct answer. Love it!

I have it at 20/4 now. Should I switch to 18/6 now then 12/12 when the autos are done?

Even though the autos will do fine under the 12/12 light schedule, from my experience, I would keep it at 18/6, if you switch it, they tend to take a little longer to finish because you took 6 hours of light away, and for autos that means 6 hours of growing has been taken away.

I have a 36×36×63 tent that has my next 5 plants in veg. Once they're done I'm putting them in the 24×48× 80 tent which has these three now in it and the dosidos purple punch will have the other one all to itself for the rest of the grow with my 1000 watt marshydro. Should I be excited about the yield or am I in over my head.

Depends. If you're 2-3 weeks from highest THC content on those autos (mostly milky trichomes, only a few ambers) then wait. Your autos still have plenty of weight to pack on the the next few weeks. If you're waiting for a couchlock harvest (25-50% amber trichomes), then you can probably flip to 12/12 now. Your autos have already done all of their fattening and you're just ripening the fruit so 12/12 won't affect them much.

Wait if you can, autoflowers seem to prefer 18-6 light schedule. This will also give you some extra time to correct any kind of problems you may be having before the flip.

HEy there Killab, so the big idea is there's nothing you can really do towards the end of your cycle to really boost your plants (with light for example), if you switch now you'll have a decent veg, any more and it's a bit of a long one. 3 months of veg is quite something though, try if if you want ! Basically THC and terpenes will degrade in light , so less light means more potent final product , towards the end folks try to have a longer dark period for that. you dont really need to do that if you're already on 12/12 the difference in bud size will be minuscule towards the end because the plant is not making flowers as much / anymore . hope this helps ! 🚀