Oh don't I know it. I forgot to plug my timer in my last grow and lost a potential ½LB plant
luckily it wasn't my only plant but it happens & it hurts lol.
Realistically with your size plants you want to water slowly untill run off and lift your plants a few times to remember the weight. Then lift them each day after to notice how quickly it becomes light. You don't want light weight pots so if you feed on Monday and it's light by Wednesday then feed every two days but that's just the start I wouldn't bother with most moisture meters. With Coco you don't even want the top of your soil to turn a lighter colour so if it does that you can probably water again.
As you mixed soil into it and the pots are Large compared to plant size we'll get into it slowly to see how the substrate/plant react and hopefully you can understand without all the meters along the way.
Stick with the Vivosun recommendation 10Ml/Gal (.9EC) and feed them every 48hrs with run off
Your kind of sat between soil & Hydro at the moment so the results will decide on which way to go.