I'm concerned that I'm about to face som...

Hi mate, just looked at her do you mean 5 gallon or 5L? If it’s 5L yes I think you should have transplanted already even though she is an auto. Although I have seen plants grow in tiny pots you will often get deficiency regardless. This is due to the plant being rootbound (check out @stuntedart on instagram). During the flowering stage especially the “stretch” she will still grow plenty of roots. Providing you transplant ASAP! You shouldn’t have to transplant more that double the size of the pot now so a 10L will be fine. It may take too long for the plant to start growing roots from the base of the main stem. So I suggest you DONT bury the current rootball to the bottom of the new pot. Step 1) Mix up some of your medium (hopfully it’s not hot soil precharged with nutrients) mix with perlite 60/40 should do. Add at least 2L of that soil mix to the bottom of a 10L pot (fabric if you can get one so quickly). Step 2) Put your root ball into the 10L pot and add the remaining soil around the sides. And water with some well oxygenated water with some 1/2 strength rooting solution. It will be normal for things to seem like they have slowed down at first but as long as you don”t shock her too much, she shouldn’t even notice the transplant! Good luck Bro✌️🏻