Normally, with super soils, I start checking ppm around 5 weeks. When you runoff tds is less than 850-900 (max), it’s time to feed.
With FF trio, it’s always best to water until about 15-20% runoff… it keeps the salts from building up and gives you something to measure tds with.
Welcome to my world.
My plants grow slow.
Indoors or out, never gets warm for seedlings or small plants.
I think your right
Winter time is great for flower around here but not so grower friendly for seedlings and early veg. I have my seedlings sitting on a heating mat at a comfy 78 
Number one bit of advice, don’t over water.
I bought one of these so I can use the ml directions