So my girls are now in week one of flower, I gave them a mini flush the other day in the form of one watering with plain RO, I then proceeded to not water for 3 days due to a lack of water (a mistake in coco I know) anyway now they are showing signs of slight yellowing leaves red stems. I have gone back to regular feeding at about 1.7 ec but am worried it will affect flower development as they are now on 12/12
Looks like either a magnesium deficiency or a copper deficiency. Cal Mag and Micro should help. Coco makes plants starve a lot for magnesium. I always mix Micro in with my Cal mag and water mix with nothing else on my water only days.
Actually, when I grow with coco, I try to water once daily. Day one is the NPK (Grow and Bloom). Day two is the Cal Mag and Micro. Day three is Silicates (Sturdy Stalk). Then repeat. Leaves don't usually recover so I always try to look at the new growth.
@southwestsmoker The farther you go along in flower the less you should use. Cal Mag and Micro can build up. These two are high in Nitrogen. To avoid getting Nitrogen toxicity, it is a good idea to start using Mag Sulfur here in a few weeks. Your leaves don't look very dark green so some extra Nitrogen won't hurt them.
Magnesium and Sulfur is found in Epsom Salt. You're in the early stages of flower so if Cal Mag is all you got for now they should be fine.
then proceeded to not water for 3 days due to a lack of water
oooof, unlucky mate! When the medium dries out the EC rises and you get an EC spike, this could be causing the issue
Looks like either a magnesium deficiency
I agree with this, its about the right time too. Coco grows will usually get a mag def on the first week of flower after a long veg. Spray with some epsom salts mate and they will be fine 
about half a teaspoon of epsom salts into 1L of water and then spray the leaves, top and bottom with a fine mister spray. They will feel much better after that
Our forum is free to join. We are an international cannabis forum that helps people all over the world grow their own personal supply of cannabis. Through our site you will find cannabis breeding forums, cannabis deficiency forums, indoor cannabis growing forums, and much more.
We are a home growers cannabis forum, and we only allow people who grow cannabis for personal use to be members. Our mission is to help you grow your own cannabis. We do not buy/sell/trade cannabis, or equipment for growing cannabis. Our site is strictly a cannabis smokers forum, cannabis growers forum and forum for medical cannabis users.
Use our guides on how to grow cannabis, cannabis grow diaries, and growers forum to find all the info you need to learn how to grow your own cannabis.
Any member who is suspected of growing cannabis for commercial gains will be banned immediately.
Please read our forum rules, and enjoy the site.
Find us on all social networks! Just search for Percys Grow Room