Hi, I have a grow room with autoflowering plants a...

NO not much they will keep on blooming but maybe strech a bit more bc they want more light.. so yeah .. its all good goodluck!

No it wont. i am actively doing this as well. it would only have adverse affects if you increased light schedule. I personally think it kicks them and resin production into over drive and it doesnt afdect yield. i havent done a side by side but i do run autos with photos so i give them the same lighting and they do just fine.

As long as you maintain same DLI, this should have little to no effect. If DLI drops, then something will suffer.. the impact will greatly be influenced by the stage of life it is in.. if the buds are already formed and fattening, the effect might not be too relevant.. maybe just takes a bit longer to finish? but, if it's during bud formation, it'll probably yield less etc... So, if going from 18h to 12h you'd want 150% of the previous power, all other factors remaining the same. Obviously distribution of light is also important. hopefully ou aren't running the light at 100% or you have additional lights to implement.

I had to do the same thing and in my experience it will effect final yield slightly but nothing significant