First off take what Thick Sticky Sock said with a big grain of salt, anyone who claims "coco is a bitch" obviously just had a bad experience with it or has never actually grown in it, coco is probably the most preferred medium amongst cannabis growers, It really falls down to your specific environment and experiences though. TSS was not entirely wrong, autos are fickle plants, they do not have the resilience that photoperiod plants have, they do not like to be transplanted so always start an auto seed in whatever container will be its final pot. You cant clone autos due to their pre-determined lifespan, a cutting taken from an auto will VERY rarely take root and if it does root it will not veg, it will become a small popcorn bud plant at its best. The only real training you can do to an auto is LST and even that can cause them to stunt if youre not careful.
Its also true that most growers will suggest you start out in soil to really learn the basics of growing before getting into any kind of hydroponic or soilless mediums, but theres nothing wrong with starting off in coco either (coco is considered a soilless medium), what you need to do though is dial in your environment, It would help if you could give us some more info like: size of your grow space,what lighting is in that grow space, how your ventilation is setup, average daily temps (high and low), your watering/feeding method, how often you are watering/feeding, and what nutes you are using. This info will give others and myself a better idea of what issues you may be running into which gives a better shot at providing you with possible solutions.
Also its good that you know coco should be between 5.5-6.5 but where are you actually adjusting it to when you mix your batch up? you should always aim for the lower side of that range to start, plants take up different nutrients at different ph levels, 5.5-5.8 is perfect ph to adjust to when mixing your nute batch for coco, the ph will naturally rise over time which gives your plants a chance to uptake nutrients across the spectrum. if your freshly mixed nute batch ph starts higher than 6.0 then you run a higher risk of your ph drifiting above 6.5 which will in turn have a negative impact on your plants, it also means your plants will not have a chance to uptake the nutrients that are only available below the 6.0 range
In conclusion, more info is needed to assess your current plant issues, Try to stick to photoperiod plants, they only take a few more weeks than autos depending on strain, grow method, etc, and are much hardier, resilient, and will produce much higher quality buds. and lastly either stick to coco and dial in your environment more, or give regular soil a try (but remember that MiracleGro is a big no-no) to really get the basics down, remember that no matter how long any of us has been growing for, we are all still learning, always keep learning, if you think your a master at this or that you have nothing left to learn then you probably have more to learn than anyone.
Peace and happy growing!
just as a quick edit since a couple of posts came in before i got mine up:
LMAO @ Xs121 you know us coco guys so well xD
and TSS is correct in his second post: promix is the bomb!